Lateral flow assay device

ABSTRACT

Lateral flow devices, methods and kits for performing lateral flow assays are provided.

This application is a continuation of U.S. application Ser. No.16/867,265, filed May 5, 2020, which is a continuation of U.S.application Ser. No. 15/818,340 filed Nov. 20, 2017, which claims thebenefit of U.S. Application 62/425,839 filed on Nov. 23, 2016, each ofwhich is hereby incorporated by reference in its entirety.

BACKGROUND

Methods for detection of immobilized analytes are commonly employed inthe biological sciences. For example, traditional blotting (e.g.,Southern, northern, western, far western, eastern, vacuum, middleeastern, eastern-western, and far-eastern blotting, etc.) can be used todetect analytes immobilized on a substrate or membrane or in a matrix(e.g., in agarose or acrylamide). In general, such blotting techniquesinvolve immobilization of the analyte(s) to be detected and contactingthe analyte(s) with a binding agent (e.g., an antibody). Blotting alsousually involves multiple washing steps and/or blocking steps betweenimmobilization and final detection. Such washing and blocking stepsconsume a practitioner's limited time and/or reagents and can be asource of error and irreproducibility.

SUMMARY

Provided herein are lateral flow assay devices and methods of using suchdevices.

In an embodiment, the lateral flow device comprises a wicking padcomposed of a porous material, the wicking pad having a planar regionfor contacting a substrate (e.g., a Western blot) comprising immobilizedanalytes (e.g., proteins); and wherein the wicking pad has a first end,a second end and two lateral edges; a base comprising two or morereservoirs spatially separated from each other, wherein each of thereservoirs receives and is in fluid communication with the first end ofthe wicking pad; and a pump comprising an absorbent pad located on thesecond end of the wicking pad. In certain embodiments, the lateral flowdevice comprises a wicking pad composed of a porous material, thewicking pad having a planar region comprising immobilized bindingagents; and wherein the wicking pad has a first end, a second end andtwo lateral edges; a base comprising two or more reservoirs spatiallyseparated from each other, wherein each of the reservoirs receives andis in fluid communication with the first end of the wicking pad; and apump comprising an absorbent pad contacting the second end of thewicking pad. In some embodiments, the lateral flow device furthercomprises a cover. In some embodiments, each reservoir has a longestdimension perpendicular to the lateral edges of the wicking pad. Incertain embodiments, one or more reservoirs have a longer dimensionparallel to the lateral edges of the wicking pad.

In some embodiments, each of the reservoirs is a depression. In someembodiments, a lowest point of one or more of the reservoirs is locatedbelow, above, or in the plane of the planar region for contacting thesubstrate. In certain embodiments, a lowest point of all of thereservoirs is located on the same plane. In some embodiments, each ofthe reservoirs comprises a length, a width and a depth. In someembodiments, each of the reservoirs spans a width of the wicking pad. Incertain embodiments, a cross-section of each of the reservoirs has ashape selected from the group consisting of a v, a semicircle, an oval,a u, a rectangle, a square, and a trapezoid. In some embodiments, eachof the reservoirs comprises a wall having a slope. In some embodiments,the reservoirs are attached to each other on at least one side. Incertain embodiments, the base is formed from molded plastic. In someembodiments, the reservoirs comprise two or more sets of reservoirsspatially separated from and adjacent to each other on a width axis ofthe lateral flow device.

In some embodiments, at least a part of the wicking pad is in intimatecontact with or is bonded to the base. In certain embodiments, at leasta part of the wicking pad is in intimate contact with or is bonded to acover. In some embodiments, the cover comprises at least two projectionseach of which project into a different reservoir. In some embodiments,each of the projections is a blade spanning the width of the reservoirinto which the blade projects. In certain embodiments, at least aportion of the wicking pad follows the contours of and is bonded to eachof the projections. In some embodiments, the wicking pad is not bondedto the base or the cover and each of the projections urge portions ofthe wicking pad into a different reservoir when the cover is placed ontothe device. In certain embodiments, at least two portions of the wickingpad are formed into protrusions each of which project into a differentreservoir when the cover is placed onto the device.

In some embodiments, the wicking pad and the pump are dry. In someembodiments, the wicking pad is wet. In some embodiments, the analytesare proteins. In some embodiments, the pump contacts an upper surface ora lower surface of the second end of the wicking pad.

In some embodiments, the wicking pad and the pump are formed of at leastone absorbent material selected from the group consisting of glassfiber, cotton, cellulose, a cellulose fiber derivative, sintered glass,sintered polymer, sintered metal, and a synthetic polymer. In someembodiments, the substrate is selected from the group consisting of amembrane, glass, plastic, silicon, metal, and metal oxide. In certainembodiments, the membrane is formed of at least one material selectedfrom the group consisting of nitrocellulose, polyvinylidene fluoride,nylon, and polysulfone. In some embodiments, the plastic is selectedfrom the group consisting of polyethylene terephthalate, polypropylene,polystyrene, and polycarbonate.

Also provided are methods of performing lateral flow assays. In someembodiments, the method comprises providing a lateral flow device asdescribed above or elsewhere herein in which the wicking pad is inintimate contact or is bonded at least in part to the base; optionallyapplying running buffer to the wicking pad; applying a substratecomprising proteins (e.g., a western blot) to the planar region forcontacting the substrate; applying a different reagent solution to eachof the reservoirs; and allowing lateral flow of the reagent solutionsfrom the reservoirs to the pump such that each of the reagents in thereagent solutions is sequentially transported in the wicking pad and iscontacted to the proteins on the substrate. In some embodiments, thereagent solutions are applied to each of the reservoirs starting with areservoir closest to the planar region for applying the substrate.

In some embodiments in which the device has a cover sealed to the base,the method further comprises removing the cover and applying runningbuffer and the substrate to the wicking pad; applying a differentreagent solution to each of the reservoirs; and placing the cover on thebase while allowing lateral flow of the reagent solutions from thereservoirs to the pump.

In some cases, the method comprises providing a lateral flow device asdescribed above or elsewhere herein in which the wicking pad is inintimate contact or is bonded at least in part to the cover; removingthe cover from the base; optionally applying a lateral flow buffer tothe wicking pad; contacting the substrate comprising proteins to theplanar region of the wicking pad for contacting the substrate; applyinga different reagent solution to each of the reservoirs starting with areservoir closest to the planar region for applying the substrate;contacting each reagent solution with the first end of the wicking padby placing the cover on the base; and allowing lateral flow of thereagent solutions from the reservoirs to the pump such that each of thereagents in the reagent solutions is sequentially transported in thewicking pad and is contacted to the proteins on the substrate. In someembodiments, the contacting each reagent solution step comprises urgingdifferent portions of the first end of the wicking pad into each of thereagent solutions with projections. In certain embodiments, thecontacting each reagent step comprises dipping the different portions ofthe first end of the wicking pad bonded to the projections into thereagent solutions. In some embodiments, the contacting each reagent stepcomprises dipping at least two protrusions near the first end of thewicking pad into the reagent solutions.

In some embodiments, the method comprises providing a lateral flowdevice as described above or elsewhere herein in which the wicking padis in intimate contact or is bonded at least in part to the cover;removing the cover from the base; optionally applying a lateral flowbuffer to the wicking pad; contacting the substrate comprising proteinsto the planar region of the wicking pad for contacting the substrate;positioning the cover on the base, thereby placing the first end of thewicking pad into each of the reservoirs; applying a different reagentsolution to each of the reservoirs starting with a reservoir closest tothe planar region for applying the substrate such that each reagentsolution contacts the different portion of the first end of the wickingpad; and allowing lateral flow of the reagent solutions from thereservoirs to the pump such that each of the reagents in the reagentsolutions is sequentially transported in the wicking pad and iscontacted to the proteins on the substrate. In some embodiments, theplacing step comprises placing a projection bonded to the wicking padinto each of the reservoirs. In certain embodiments, the placing stepcomprises urging the different portion of the first end of the wickingpad into each of the reservoirs with a projection. In some embodiments,the placing step comprises placing a protrusion formed from the wickingpad into each of the reservoirs. In some embodiments, the applying adifferent reagent solution to each of the reservoirs step comprisesapplying the reagent solution through a port in each of the reservoirsor in the cover.

In some embodiments, the different reagent solutions are applied to thereservoirs sequentially or simultaneously. In some embodiments, thecontacting the substrate comprising proteins to the planar region of thewicking pad for contacting the substrate step comprises contacting anupper surface or a lower surface of the wicking pad.

In some embodiments, the allowing lateral flow step comprises allowingprimary antibodies from a first reagent solution in a first reservoir tobind to their target proteins, if present, on the substrate, followed byallowing a first wash solution from a second reagent solution in asecond reservoir to remove unbound primary antibodies from thesubstrate. In some embodiments, the allowing lateral flow step furthercomprises allowing secondary antibodies or a secondary detection reagentfrom a third reagent solution in a third reservoir to contact theprimary antibodies bound to their target proteins, if present, on thesubstrate. In some embodiments, the allowing lateral flow step furthercomprises allowing a second wash solution from a fourth reagent solutionin a fourth reservoir to remove unbound secondary antibodies from thesubstrate.

In some embodiments, the volume of the second wash solution is at leasttwice the volume of the third reagent solution having the secondaryantibody. In certain embodiments, the method further comprises followingbinding of the primary antibodies to the target proteins if present,optionally following contact of secondary antibodies or secondarydetection reagents to the primary antibodies, optionally removing thesubstrate, and detecting the binding of the primary antibodies to thetarget proteins if present.

In certain embodiments, the method comprises providing a lateral flowdevice as described above or elsewhere herein in which binding agentsare immobilized on a planar region of the wicking pad; optionallyapplying a lateral flow buffer to the wicking pad; applying a differentsolution to at least two of the reservoirs starting with a reservoirclosest to the planar region of the wicking pad comprising immobilizedbinding agents; and allowing lateral flow of the solutions from thereservoirs to the pump such that the solutions are sequentiallytransported in the wicking pad and are contacted to the proteinsimmobilized on the wicking pad. In some embodiments in which the devicehas a cover attached to the base, the method further comprises removingthe cover; optionally applying lateral flow buffer to the wicking pad;applying a different solution to each of the reservoirs starting withthe reservoir closest to the planar region of the wicking pad havingimmobilized binding agents; and placing the cover on the base whileallowing lateral flow of the different solutions from the reservoirs tothe pump.

In some embodiments, the method comprises providing a lateral flowdevice as described above or elsewhere herein in which binding agentsare immobilized on a planar region of the wicking pad and in which thewicking pad is in intimate contact or is bonded at least in part to thecover; removing the cover from the base; optionally applying a lateralflow buffer to the wicking pad; applying a different solution to each ofthe reservoirs starting with a reservoir closest to the planar region ofthe wicking pad having immobilized binding agents; contacting eachsolution with the first end of the wicking pad by placing the cover onthe base; and allowing lateral flow of the solutions from the reservoirsto the pump such that the solutions are sequentially transported in thewicking pad and are contacted to the binding agents immobilized on thewicking pad. In some embodiments, the contacting each solution stepcomprises urging different portions of the first end of the wicking padinto each of the solutions with projections. In some embodiments, thecontacting each solution step comprises dipping the different portionsof the first end of the wicking pad bonded to the projections into thesolutions. In some embodiments, the contacting each solution stepcomprises dipping at least two protrusions near the first end of thewicking pad into the solutions.

In some embodiments, the method comprises providing a lateral flowdevice as described above or elsewhere herein in which binding agentsare immobilized on a planar region of the wicking pad and in which thewicking pad is in intimate contact or is bonded at least in part to thecover; removing the cover from the base; optionally applying a lateralflow buffer to the wicking pad; positioning the cover on the base,thereby placing the first end of the wicking pad into each of thereservoirs; applying a different solution to each of the reservoirsstarting with a reservoir closest to the planar region havingimmobilized binding agents such that each solution contacts thedifferent portion of the first end of the wicking pad; and allowinglateral flow of the solutions from the reservoirs to the pump such thateach of the solutions is sequentially transported in the wicking pad andis contacted to the binding agents on the substrate. In someembodiments, the placing step comprises placing a projection bonded tothe wicking pad into each of the reservoirs. In some embodiments, theplacing step comprises urging the different portion of the first end ofthe wicking pad into each of the reservoirs with a projection. Incertain embodiments, the placing step comprises placing a protrusionformed from the wicking pad into each of the reservoirs. In someembodiments, the applying a different solution to each of the reservoirsstep comprises applying each of the solutions through a port in each ofthe reservoirs or in the cover.

In some embodiments in which binding agents are immobilized on a planarregion of the wicking pad, the solution is a sample having an analyte(and optionally, a control protein) therein or a reagent solution havinga reagent therein. In some embodiments, the different solutions areapplied to the reservoirs sequentially or simultaneously. In someembodiments, the allowing lateral flow step comprises allowing theanalytes from the sample in a first reservoir to bind to at least onebinding agent immobilized on the wicking pad, followed by allowing afirst wash solution in a second reservoir to remove unbound materialfrom the wicking pad. In certain embodiments, the allowing lateral flowstep comprises allowing the analyte, if present, to bind to a reversiblyimmobilized labeled first primary antibody (e.g., a primary antibodyconjugate) followed by allowing the complexed analyte to bind to anunlabeled second primary antibody irreversibly immobilized downstreamfrom the first primary antibody. In some embodiments, the method furthercomprises following binding of the analyte, if present, to the firstprimary antibody and the second primary antibody, and detecting thebinding of the analyte, if present, to the first and second primaryantibodies (e.g., detecting the analyte sandwiched between the first andsecond primary antibodies).

In certain embodiments, the methods further comprise applying asubstantially uniform pressure to the pump.

Also provided is a kit for performing lateral flow. In some embodiments,the kit comprises the lateral flow device as described above andelsewhere herein. In some embodiments, the kit includes a plurality ofabsorbent pads for use as a pump, all of which are described herein. Insome embodiments, the kit includes reagents (e.g., binding agentsincluding labeled primary antibody or primary and secondary antibodies,wash solution, and/or running buffer) provided as solutions to beapplied to the reservoirs by the end-user. In certain embodiments, someor all of the reagents are dried onto the wicking pad in the portions ofthe wicking pad in fluid communication with each of the reservoirs ofthe device.

In some embodiments, the kit further includes running buffer forperforming lateral flow and optionally includes blocking agents (e.g.,bovine serum albumin, non-fat dried milk, or casein), surfactants (e.g.,Tween 20 or Triton X-100), protein aggregation modifying agents asdescribed herein, macromolecular crowding agents (e.g., dextran,polyethylene glycol and/or Ficoll), density agents and/or agents topromote even flow of reagents and/or promote reaction to molecules onthe substrate and minimize background on the substrate. The additionalagents can be provided in the kit as a solid or in liquid form. In someembodiments, the kit further includes instructions for carrying out themethods described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional side view of a lateral flow deviceaccording to an embodiment. The device includes a base having fourreservoirs that sequentially deliver reagent solutions to a wicking padin intimate contact with the base. The wicking pad follows the contoursof the reservoirs. The lowest point of each reservoir is below the planeof the planar region of the wicking pad onto which a substrate isplaced. The cross-sectional shape of each reservoir is a “V”. The deviceis shown with the substrate in intimate contact with the wicking pad.

FIG. 2 is a schematic cross-sectional side view of a lateral flow deviceaccording to an embodiment. In this embodiment, the lowest point of eachreservoir is below the plane of the planar region of the wicking padonto which the substrate is placed. The cross-sectional shape of eachreservoir is a “V”.

FIG. 3 is a schematic cross-sectional side view of a lateral flow deviceaccording to an embodiment in which the lowest point of each reservoiris above the plane of the planar region of the wicking pad onto whichthe substrate is placed. The cross-sectional shape of each reservoir isa “V”.

FIGS. 4A and 4B are top and side perspective views, respectively, of alateral flow device according to an embodiment in which the lowest pointof each reservoir is below the planar region of the wicking pad ontowhich the substrate is placed. The cross-sectional shape of eachreservoir is a “V”. In this embodiment, the wicking pad is substantiallyentirely bonded to the plastic molded base which is the base of thedevice.

FIGS. 5A and 5B are top and side perspective views, respectively, of alateral flow device according to an embodiment in which thecross-sectional shape of each reservoir is a semi-circle. In thisembodiment, a lowest point of each reservoir is on the same plane as theplanar region of the wicking pad onto which the substrate is placed.FIG. 5A shows a substrate and a pump in intimate contact with thewicking pad. The wicking pad is substantially entirely bonded to theplastic molded base which is the base of the device.

FIGS. 6A and 6B are top and side perspective views, respectively, of alateral flow device according to an embodiment in which thecross-sectional shape of each reservoir is a semi-circle. In thisembodiment, a lowest point of each reservoir is below the plane of theplanar region of the wicking pad onto which the substrate is placed.FIG. 6A shows a substrate and a pump in intimate contact with thewicking pad. The wicking pad is substantially entirely bonded to theplastic molded base which is the base of the device.

FIGS. 7-10 are schematic side views of lateral flow devices according toembodiments. In each embodiment, the cross-sectional shape of eachreservoir is a square. The wicking pad is partially in intimate contactwith the base (i.e., the wicking pad does not follow the contours of thereservoirs). In FIGS. 7 and 8 , a lowest point of each reservoir isbelow the planar region of the wicking pad onto which the substrate isplaced. In FIGS. 9 and 10 , a lowest point of each reservoir is on thesame plane as the planar region of the wicking pad onto which thesubstrate is placed. In FIGS. 7 and 9 , the reservoirs are attached toeach other on at least one side. In FIGS. 8 and 10 , the reservoirs arenot attached to each other on at least one side. The devices in FIGS.7-10 are shown without a pump.

FIG. 11 is a schematic cross-sectional side view of a lateral flowdevice according to an embodiment in which the wicking pad is at leastpartially bonded to a cover. The wicking pad follows the contours and isbonded to projections that project into the reservoirs (shown withreagent solution therein) when the cover is placed onto the device.

FIGS. 12-14 are schematic cross-sectional side views of lateral flowdevices according to embodiments in which the wicking pad is at leastpartially bonded to a cover. Portions of the wicking pad are formed(e.g., folded) into protrusions that project into the reservoirs (shownwith reagent solution therein) when the cover is placed onto the device.In FIG. 12 , sections of the wicking pad between the protrusions arebonded to the cover. In FIGS. 13 and 14 , sections of the wicking padbetween the protrusions are bonded to the base at edges between thereservoirs.

FIG. 15 is a schematic perspective view of a lateral flow deviceaccording to an embodiment in which binding agents are immobilized on aplanar region of the wicking pad downstream from the reservoirs.

FIG. 16 is a perspective view of a lateral flow device according to anembodiment comprising a plurality of sets of reservoirs. The device canbe used to analyze multiple substrates simultaneously. The device isshown with no substrate or pump.

FIGS. 17A-17E are perspective views of the lateral flow device of FIGS.4A and 4B during various stages of operation and as described inExample 1. The solutions emptied from the reservoirs into the wickingpad in sequential order starting at reservoir 1 and ending withreservoir 4. The portion of the device having the pump is not shown inthe views.

FIGS. 18A-18C are immunoblotting results using the lateral flow deviceof FIGS. 4A and 4B and as described in Example 2.

DETAILED DESCRIPTION

Described herein are lateral flow devices and methods of using suchdevices that allow for efficient lateral flow detection of analytes(e.g., proteins, nucleic acids) immobilized on substrates (e.g., westernblot membranes) or the wicking pad (e.g., a diagnostic application)using specific binding agents (e.g., antibodies). The devices andmethods described herein also allow for efficient lateral flow detectionof analytes captured by specific binding agents immobilized onsubstrates. Lateral flow devices and methods of using such devices havebeen discovered that deliver different solutions (e.g., samples havingone or more analytes, specific binding agents, running buffer, washsolutions) sequentially and hands-free to a wicking pad in intimatecontact with a substrate having analytes or binding agents immobilizedthereon. The solutions are delivered sequentially to the wicking padfrom at least two reservoirs molded into the base of the lateral flowdevices. In some embodiments, the devices described herein can beconfigured in a single-use device, allowing for an affordable and simpleassay format.

1. DEFINITIONS

The term “analyte” refers to a biological molecule, e.g., a protein,nucleic acid, polysaccharide, lipid, antigen, growth factor, hapten,etc., or a portion thereof. Analytes can be reversibly or irreversiblyimmobilized on a surface, such as a membrane or a wicking pad anddetected as described herein.

The term “immobilized” or “embedded” interchangeably refers toreversibly or irreversibly immobilized molecules (e.g., analytes orbinding agents). In some embodiments, reversibly immobilized moleculesare immobilized in a manner that allows the molecules, or a portionthereof (e.g., at least 25%, 50%, 60%, 75%, 80% or more of themolecules), to be removed from their immobilized location withoutsubstantial denaturation or aggregation. For example, a molecule can bereversibly immobilized in or on an absorbent material (e.g., anabsorbent pad) by contacting a solution containing the molecule with theabsorbent material, thereby soaking up the solution and reversiblyimmobilizing the molecule. The reversibly immobilized molecule can thenbe removed by wicking the solution from the absorbent material, or fromone region of the absorbent material to another. In some cases, amolecule can be reversibly immobilized on an absorbent material bycontacting a solution containing the molecule with the absorbentmaterial, thereby soaking up the solution, and then drying thesolution-containing absorbent material. The reversibly immobilizedmolecule can then be removed by contacting the absorbent material withanother solution of the same or a different composition, therebysolubilizing the reversibly immobilized molecule, and then wicking thesolution from the absorbent material, or from one region of theabsorbent material to another.

Irreversibly immobilized molecules (e.g., binding agents or analytes)are immobilized such that they are not removed, or not substantiallyremoved, from their location under mild conditions (e.g., pH betweenabout 4-9, temperature of between about 4-65° C.). Exemplaryirreversibly immobilized molecules include protein analytes or bindingagents bound to a nitrocellulose, polyvinylidene fluoride, nylon orpolysulfone membrane by standard blotting techniques (e.g.,electroblotting). Other exemplary irreversibly immobilized moleculesinclude protein analytes or binding agents bound to glass or plastic(e.g., a microarray, a microfluidic chip, a glass histology slide or aplastic microtiter plate having wells with bound protein analytestherein).

The term “binding agent” refers to a agent that specifically binds to amolecule such as an analyte. While antibodies are described in manycontexts herein, it will be understood that other binding agents can beused instead of antibodies as preferred by the user. A wide variety ofbinding agents are known in the art, including antibodies, aptamers,affimers, lipocalins (e.g., anticalins), thioredoxin A, bilin bindingprotein, or proteins containing an ankyrin repeat, the Z domain ofstaphylococcal protein A, or a fibronectin type III domain. Otherbinding agents include, but are not limited to, biotin/streptavidin,chelating agents, chromatography resins, affinity tags, orfunctionalized beads, nanoparticles and magnetic particles.

The term “specifically bind” refers to a molecule (e.g., binding agentsuch as an antibody or antibody fragment) that binds to a target with atleast 2-fold greater affinity than non-target compounds, e.g., at least4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold, 10-fold, 20-fold,25-fold, 50-fold, 100-fold, or 1000-fold or more greater affinity.

The term “antibody” refers to a polypeptide comprising a frameworkregion from an immunoglobulin gene, or fragments thereof, thatspecifically bind and recognize an antigen, e.g., a particular analyte.Typically, the “variable region” contains the antigen-binding region ofthe antibody (or its functional equivalent) and is most critical inspecificity and affinity of binding. See Paul, Fundamental Immunology(2003). Antibodies include for example chimeric, human, humanizedantibodies, or single-chain antibodies.

An exemplary immunoglobulin (antibody) structural unit comprises atetramer. Each tetramer is composed of two identical pairs ofpolypeptide chains, each pair having one “light” (about 25 kD) and one“heavy” chain (about 50-70 kD). The N-terminus of each chain defines avariable region of about 100 to 110 or more amino acids primarilyresponsible for antigen recognition. The terms variable light chain(V_(L)) and variable heavy chain (V_(H)) refer to these light and heavychains respectively.

Antibodies can exist as intact immunoglobulins or as any of a number ofwell-characterized fragments that include specific antigen-bindingactivity. Such fragments can be produced by digestion with variouspeptidases. Pepsin digests an antibody below the disulfide linkages inthe hinge region to produce F(ab)′₂, a dimer of Fab which itself is alight chain joined to V_(H)-C_(H)1 by a disulfide bond. The F(ab)′₂ maybe reduced under mild conditions to break the disulfide linkage in thehinge region, thereby converting the F(ab)′₂ dimer into an Fab′ monomer.The Fab′ monomer is essentially Fab with part of the hinge region (seeFundamental Immunology (Paul ed., 3d ed. 1993). While various antibodyfragments are defined in terms of the digestion of an intact antibody,one of skill will appreciate that such fragments may be synthesized denovo either chemically or by using recombinant DNA methodology. Thus,the term antibody, as used herein, also includes antibody fragmentseither produced by the modification of whole antibodies, or thosesynthesized de novo using recombinant DNA methodologies (e.g., singlechain Fv) or those identified using phage display libraries (see, e.g.,McCafferty et al., Nature 348:552-554 (1990)).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used herein, the term “about” refers tothe recited number and any value within 10% of the recited number. Thus,“about 5” refers to any value between 4.5 and 5.5, including 4.5 and5.5.

II. DEVICES

FIGS. 1-15 illustrate embodiments of lateral flow devices for detectinganalytes on a substrate, for detecting analytes bound to binding agentson a substrate, or for detecting analytes bound to binding agents on awicking pad.

Referring to FIGS. 1 and 4A-4B, a lateral flow device 100 includes awicking pad 102 having a first end 104, a second end 106, two lateraledges 108, and a planar region 110 for contacting a substrate 112 (e.g.,a membrane) comprising immobilized analytes or proteins (e.g., a westernblot, a dot blot) to be detected. The lateral flow device 100 alsoincludes a base 114 comprising two or more reservoirs 116 (e.g.,depressions or troughs) spatially separated from each other. In someembodiments, each reservoir has a longest dimension perpendicular to thelateral edges 108 of the wicking pad 102. Each reservoir is thereforeoriented perpendicular to the direction of lateral flow. In certainembodiments, one or more reservoirs have a longer dimension parallel tothe lateral edges of the wicking pad 102. The reservoirs 116 (e.g., R1,R2, R3, and R4) are located at or near the first end 104 of the wickingpad 102. Each of the reservoirs 116 receives and is in fluidcommunication with the first end 104 of the wicking pad 102 (i.e.,liquid, when present in the reservoirs 116, can flow from each of thereservoirs 116 into the wicking pad 102). The reservoirs 116 supplyliquid (e.g., buffers and detection reagents) sequentially to thewicking pad 102 and into the planar region 110 for applying thesubstrate 112. The planar region 110 is located downstream from thereservoirs 116 and upstream from a pump 120 (e.g., between thereservoirs 116 and the pump 120). The pump 120 is located on or adjacentto the second end 106 of and in intimate contact with the wicking pad102. The dry pump 120 acts as a drain by wicking the liquid from thereservoirs 116 through the wicking pad 102.

Each of the reservoirs is bounded by a first wall 117 and a second wall118 oriented perpendicular to the flow of liquid. Each of the reservoirsis further bounded by two end walls 119. In some embodiments, an edge ofthe second wall 118 of a first reservoir R1 is attached to an edge ofthe first wall 117 of a second reservoir R2. In certain embodiments, thereservoirs share a wall. For example, the second wall of the firstreservoir R1 can be the first wall of the second reservoir R2 (e.g.,FIGS. 7 and 9 ). In some embodiments, the reservoirs are not attached toeach other, nor do the reservoirs share a wall (FIGS. 8 and 10 ).

In some embodiments, each of the reservoirs 116 spans the width of thewicking pad 102. In some embodiments, a lowest point of one or more ofthe reservoirs is located substantially below the plane of the planarregion 110 of the wicking pad 102 (see FIGS. 1-2, 4A-4B, 6A-6B, 7-8,11-15 ). In certain embodiments, the lowest point of one or more of thereservoirs 116 is located substantially in the plane of the planarregion 110 (see FIGS. 5A-5B, 9-10 ). In some embodiments, the lowestpoint of one or more of the reservoirs 116 is located substantiallyabove the plane of the planar region 110 (see FIG. 3 ). In certainembodiments, the lowest point of all of the reservoirs 116 is located onthe same plane which can be on, above or below the plane of the planarregion 110.

Referring again to FIGS. 1 and 4A-4B, the reservoirs 116 can be any sizeand shape. In some embodiments, each of the reservoirs 116 comprises alength L1, a width W1, and a depth D1. In some embodiments, each of thereservoirs is at least about 0.1, 0.5, 1.0, 8.5, 13.5, 20 cm or more inat least one dimension. In some cases, the length L1 and the width W1 ofeach of the reservoirs 116 are at least about 2-fold, 3-fold, 5-fold,10-fold, 100-fold or more larger than the depth D1. In some embodiments,each of the reservoirs is sized to match the width of the wicking pad102 and has a width W1 that is at least about 3-fold, 4-fold, 5-fold,6-fold, 8-fold, 10-fold, 13-fold, 17-fold, 20-fold, 27-fold or morelarger than the length L1. Exemplary sizes of each reservoir include,but are not limited to, about 0.5 cm×8.5 cm, 1×3 cm, 3 cm×3 cm, 2.5cm×about 8.5 cm, 1 cm×10 cm, 3 cm×10 cm, 2 cm×13.5 cm, 3×13.5 cm, 1cm×15 cm, 3 cm×15 cm, or 3.5 cm×20 cm in length L1 and width W1,respectively. As shown in FIGS. 1-17E, the “length L1” is based on thedirection of flow and is the shortest dimension. In some embodiments,each reservoir is 3 cm in length L1 by 10 cm in width W1. In some cases,each reagent reservoir is 1±0.5, 1, 2 or 3 cm in length L1 by 10±0.5 cmor 15±0.5 cm in width W1. In some cases, the length L1 is the longerdimension and one or more of the reservoirs is about 1 cm to about 5 cmin length L1 by about 0.5 cm to about 5 cm in width W1. In some cases,the depth D1 of at least one reservoir is about 0.5 cm, about 1 cm,about 2 cm, or about 3 cm.

In certain embodiments, a cross-section of each of the reservoirs 116has a “V” shape (FIGS. 1-3, 4A-4B), a semicircle shape (FIGS. 5A-6B), anoval shape, a “U” shape, a rectangle shape, a square shape (FIGS. 7-10), or a trapezoid shape (FIGS. 11-15 ). In some embodiments, the firstwall 117 and the second wall 118 of each of the reservoirs 116 has aslope ranging from about 30 degrees to about 90 degrees relative to ahorizontal plane. In certain embodiments, the end walls 119 of each ofthe reservoirs 116 have a slope of about 90 degrees relative to ahorizontal plane. The depth D1 of the reservoirs 116 and the slope ofthe first and second walls can be chosen to control the overall flowrate of reagent solutions exiting the reservoirs 116, with deeperdepressions or steeper walls slowing the lateral flow rate and moreshallow sloped walls resulting in faster flow rates. The volume of eachof the reservoirs 116 is determined by many factors including, but notlimited to, the size and shape of the reservoirs 116 and theconfiguration of the lateral flow device 100. In some embodiments, eachreservoir has a capacity of at least about 0.1 milliliters to about 30milliliters.

As shown in FIGS. 4A-6B, the reservoirs 116 comprise one set of fourreservoirs. In some embodiments (FIG. 16 ), the reservoirs comprise twoor more sets 1640 of reservoirs spatially separated from each other(e.g., separated by a wall or a distance) such that multiple substratescan be analyzed at one time. In some embodiments, the sets 1640 ofreservoirs are adjacent to each other on the width axis of the lateralflow device 1640. The sets 1640 of reservoirs are arranged to run inparallel to each other in a side-by-side relationship. Each set ofreservoirs is functionally independent of the adjacent set ofreservoirs.

In embodiments having sets of reservoirs, one or more dividing walls1642 between the sets of reservoirs can be molded into the base 1614 ofthe lateral flow device 1600 as shown in FIG. 16 . In some embodiments,the dividing walls 1642 are formed by inserting/attaching a barrier tothe base 1614 using adhesive, silicone, or caulking. In someembodiments, the dividing walls 1642 are formed by inserting one or morewalls into compatible slots in the base 1614. Barriers may be formedfrom wax or acrylic that is printed or deposited in one or more layersto create a desired barrier height. The barrier can also be made of ahydrophobic or impermeable material (e.g., wax, acrylic, silicone) toprevent flow of aqueous solutions between the sets of reservoirs. Insome embodiments, the barrier extends from the first end 104 of thewicking pad 102 to the planar region 1610 for applying the substrate. Incertain embodiments, the barrier(s) extend from the reservoirs to theend of the planar region 1610 to inhibit, eliminate, or substantiallyeliminate fluid communication (e.g., fluid flow) between adjacent zonesin the wicking pad and allow for simultaneous processing of multiplesubstrates. In some embodiments, the barrier extends from the first end104 to the second end 106 of the wicking pad 102 (i.e., substantiallythe entire length of the wicking pad). In an embodiment in which thebarrier does not extend to the second end 106 of the wicking pad 102, asingle pump can extend across the width of the second end of the wickingpad and can be used to process multiple substrates. In embodiments inwhich the barriers extend from the first end to the second end of thewicking pad, each zone of the wicking pad can have a separate pump. Insome embodiments, barriers can be a mix of different formats. Forexample, the reservoir sets can be separated via a molded dividing walland zones downstream from the reservoirs can be separated by a waxbarrier or a region in which the wicking pad has been removed from thebase to form a gap between the zones. When the lateral flow device is inuse, the barriers or gaps in the wicking pad help to control the fluidflow in a linear direction to the pump.

Hydrophobic barriers include, but are not limited to, wax barriers, orbarriers created by vapor or liquid phase silanization of the wickingpad. Exemplary materials from which impermeable barriers can be formedinclude, but are not limited to, wax, plastic, polymers, and resin.

The wax used to form the wax barriers can be any wax that is flowable atelevated temperatures and non-flowable at ambient temperature (e.g.,about 20-25° C.). Examples are paraffin waxes, microcrystalline waxes,thermoset waxes, animal waxes such as beeswax, lanolin, and tallow,vegetable waxes such as soy, carnauba, candelilla and palm waxes,mineral waxes such as ceresin and montan waxes, petroleum waxes, andsynthetic waxes such as ethylenic polymers, chlorinated naphthalenes,and Fischer-Tropsch waxes. Paraffin wax compositions may contain, inaddition to n-paraffins and isoparaffins, minor amounts ofcyclo-paraffins or olefins, or both. Waxes that become flowable, i.e.,that have melting points, within the temperature range of from about 60°C. to about 150° C., or from about 75° C. to about 125° C., are amongthose that can be used. Wax formulations and compositions that behave inthis manner are known to those of skill in the art.

The silanization reagent used to form hydrophobic barriers can be anysilanization reagent that reacts with the wicking pad, or a portionthereof. For example, if the wicking pad contains cellulose, asilanization reagent that silanizes hydroxyl groups of the cellulosebackbone can be utilized. Exemplary silanization reagents include, butare not limited to, trimethylchlorosilane, trimethylsilane, orhexamethyldisilazane. Silanization reagents further includetriethoxysilanes (R—Si(C2HSO)3) where R is, for example, vinyl,methacrylol, aminopropyl, fluoroalkyl, or thioethyl. Other suitablesilanization reagents will be readily apparent to those of skill in theart. Polymers can be reacted with the silane groups to create animpermeable barrier.

The wax or other barrier forming reagent (e.g., silanization reagent, orimpermeable barrier) can be applied to one side or both sides of thewicking pad, although in most cases, application to one side will besufficient, provided that the wax or reagent penetrates, or is made topenetrate (e.g., by melting after application), the wicking pad to adegree sufficient to serve as a barrier to the flow of liquid. Thebarrier forming reagent can be applied as a liquid. The liquid can beapplied by hand or other apparatus. In some cases, the liquid is sprayedor poured onto the wicking pad. Spraying can be accomplished with aninkjet printer or similar apparatus. In some cases, the liquid hardensafter application to form an impermeable and/or hydrophobic barrier.Alternatively, the barrier forming reagent can be applied as a vapor.For example, a silanization reagent, wax, plastic, resin, or polymer canbe applied as a vapor that condenses on the wicking pad or reacts withthe wicking pad. Alternatively, the barrier forming reagent can beapplied as a solid. For example, wax can be applied as a solid manuallyor in an automated or mechanized fashion. In some cases, the wicking padis masked to protect regions from the barrier forming reagent, and thebarrier forming reagent is contacted with the wicking pad.

Application of wax can be achieved by hand, either by the use of acommon crayon or by a wax pen, or by a wax printer. Wax pens are knownin the art and commonly include a housing having a reservoir to containhot wax, a spout, and a handle. Application of the hot wax is achievedby tipping the housing to cause the liquefied wax to pass through thespout, and the housing is equipped with a valve to stop the flow of thewax at the terminus of a printed line.

Wax printers are likewise known in the art and commonly operated bythermal transfer printing using a print head that includes an array ofvery small heating elements that are software-controlled for independentactivation to produce localized heating of the wax above its meltingpoint to release the wax to the print medium. Commercially availableexamples of wax printers include the Phaser 8560DN (Fuji Xerox, Ltd.,Japan), and the CALCOMP COLORMASTER PLUS thermal wax transfer printer(CalComp Graphics, LLC, Foothill Ranch, Calif., USA).

In some embodiments, once applied, the wax can be made to penetrate thebulk thickness of the wicking pad to fill the pores and form a lateralbarrier to aqueous fluid flow by heating the wax above its meltingpoint. In some cases, the amount of wax applied will be such that fullpenetration of the thickness of the wicking pad with the melted wax willoccur while lateral flow of the melted wax (i.e., in directions parallelto the lateral edges of the wicking pad) is minimal or at least limitedto a small distance that is substantially uniform along the length of aline of applied wax so that the resulting area bordered by the waxbarrier is known and controlled. The formation of the barrier in thismanner can also be controlled by the degree of heating, including thetemperature to which the wax is heated and the length of time that theheating is continued. Optimal temperatures and durations are readilydeterminable by routine trial and error, but in most cases serviceableresults will be obtained by heating to at least 5° C. above the waxmelting point, and in many cases from about 5 to about 50° C. above themelting point, or from about 10 to about 30° C. above the melting point.The most appropriate heating time will depend on the temperature, highertemperatures requiring less time. In general, heating times ranging fromabout fifteen seconds to about twenty minutes, or in many cases fromabout thirty seconds to about ten minutes, will provide useful results.Heating can be achieved by conventional means, including radiativeheating, conductive heating, convective heating, impulse heating, andmicrowave heating. Effective results can be achieved with equipment assimple as a hot plate or a conventional oven.

The width of each of the reservoirs in the sets will depend on therequired number of sets of reservoirs and the width of the wicking pad.In some embodiments having multiple sets of reservoirs, the width of thereservoir is about 3 mm to about 3 cm. Likewise, the dividing walls orbarriers can be any thickness as long as they prevent crosscommunication of reagents placed into adjacent reservoirs. Optimalwidths for hydrophobic or impermeable barriers may vary with thedimensions of the area to be bordered by the barrier and with thethickness of the wicking pad and are readily determinable by routinetesting. In most cases, the width will range from about 10 microns toabout 5 mm, from about thirty microns to about 3 mm, from about 100microns to about 1 mm, or from about 200 microns to about 5 mm, or 10mm.

In certain embodiments, the wicking pad 102 is substantially entirely inintimate contact with an upper surface of the base and follows thecontours of the base (FIGS. 1-6B). In some embodiments, the wicking pad102 is not bonded to the end walls 119 of the reservoirs. In certainembodiments, the wicking pad 102 is substantially entirely bonded to anupper surface of the base (FIGS. 1-6B). In some embodiments, a part ofthe wicking pad 102 (e.g., the portion in fluid communication with eachof the reservoirs 116) is in intimate contact with or is bonded to theupper surface 122 of the base 114 and follows the contours of the firstand second walls 117, 118 of each of the reservoirs 116. In certainembodiments, only the planar region 110 and the second end 106 arebonded to the upper surface of the base (FIGS. 7-10 ). Bonding thewicking pad 102 to the upper surface of the base can prevent fluid flowon the underside of the wicking pad 102.

Lateral flow devices having a cover that covers or attaches to the baseare illustrated in FIGS. 11-15 . Each of the lateral flow devices 1100,1200, 1300, 1400, 1500 includes a wicking pad 102 having a first end104, a second end 106, two lateral edges 108, and a planar region 110for contacting a substrate 112 comprising immobilized analytes orproteins to be detected. Each of the lateral flow devices 1100, 1200,1300, 1400, 1500 also include a base 1114, 1214, 1314, 1414, 1514comprising two or more reservoirs 1116, 1216, 1316, 1416, 1516 (e.g,depressions or troughs) spatially separated from each other. Eachreservoir has a longest dimension perpendicular to the lateral edges ofthe wicking pad. The reservoirs 1116, 1216, 1316, 1416, 1516 are locatedat or near the first end 104 of the wicking pad 102. Each of thereservoirs 1116, 1216, 1316, 1416, 1516 receives and is in fluidcommunication with the first end 104 of the wicking pad 102 (i.e.,liquid, when present in the reservoirs 1116, 1216, 1316, 1416, 1516 canflow from each of the reservoirs 1116, 1216, 1316, 1416, 1516 to thewicking pad 102). The reservoirs 1116, 1216, 1316, 1416, 1516 supplyliquid (e.g., buffers and detection reagents) sequentially to thewicking pad 102 and into the planar region 110 for applying thesubstrate 112. Each of the reservoirs is bounded by a first wall 1117,1217, 1317, 1417, 1517 and a second wall 1118, 1218, 1318, 1418, 1518oriented perpendicular to the flow of liquid. Each of the reservoirs isfurther bounded by two end walls. In some embodiments, an edge of thesecond wall 1118, 1218, 1318, 1418, 1518 of a first reservoir R1 isattached to an edge of the first wall of a second reservoir R2.

In some embodiments, the lateral flow device 1100 includes a cover 1124having two or more projections 1126 each of which projects into adifferent reservoir (FIG. 11 ). The projections 1126 can be sized toproject partially or completely into the reservoirs when the cover 1124is placed onto the device 1100. For example, a tip of each of theprojections 1126 can be in close proximity to the bottom of thereservoirs when the cover is placed on the device. In some embodiments,each of the projections 1126 is a blade spanning the width of thereservoir into which the blade projects.

In certain embodiments having a cover, the wicking pad 102 is inintimate contact with all or part of a lower surface 1128, 1228, 1328,1428 of the cover 1124, 1224, 1324, 1424 (FIGS. 11-14 ). For example, asillustrated in FIG. 11 , the wicking pad can follow the contours of thecover 1120 including the projections 1126 such that the wicking padcontacts reagent solution 1130 in the reservoirs when the cover 1124 isplaced on the device 1100. In some embodiments, all or a part of thewicking pad 102 is bonded to the cover. For example, the wicking pad 102can be bonded to all or part of the projections 1126 in the cover 1124.In certain embodiments, the wicking pad 102 is not bonded to the coverand the projections urge the wicking pad into the reservoirs when thecover is placed on the device 1100. In some embodiments, the wicking pad102 is bonded only to the cover in the planar region 110 that contactsthe substrate 112 (FIGS. 12-14 ).

As shown in FIGS. 11-14 , a lower surface of the wicking pad contactsthe substrate 112. In an embodiment in which the wicking pad 102 is notbonded nor is in intimate contact with the cover, the substrate 112 cancontact an upper or lower surface of the wicking pad 102. As illustratedin FIG. 15 , in an embodiment not having a substrate and in whichbinding agents (e.g., BA1, BA2, and BA3) are immobilized (e.g. areprinted in lines or spots) on or in planar region 110 of the wicking pad102 (e.g. an embodiment used in a diagnostic assay), a lower surface ofthe planar region 110 is in intimate contact or is bonded to the base.

As illustrated in FIGS. 12-15 , portions of the wicking pad 102 near thefirst end 104 can be folded such that protrusions 105 are formed in thewicking pad 102. The protrusions 105 dip into the reservoirs when thecover is placed onto the device. When the cover is placed onto thedevice, the protrusions 105 contact the reagent solutions, when present,in the reservoirs. Sections of the wicking pad 102 between theprotrusions 105 can contact or be bonded to the cover (FIG. 11 ) or thebase (FIGS. 12-14 ).

The lateral flow devices 1100, 1200, 1300, 1400, 1500 further include apump 1120, 1220, 1320, 1420, 1520 located on or adjacent to the secondend 106 of and in intimate contact with the wicking pad 102. The pump1120, 1220, 1320, 1420, 1520 can contact an upper surface (FIGS. 11-13 )or a lower surface (FIGS. 14 and 15 ) of the second end 106 of thewicking pad 102. The pump 1120, 1220, 1320, 1420, 1520 can further besubstantially entirely contained in the cover or the base of the device.

The planar region 110 of the wicking pad 102 can includedrawings/markings or other indications for where a user should place thesubstrate 112 or where binding agents are immobilized in/on the wickingpad. Alternately, the drawing/markings can be on the device cover orbase.

The wicking pad 102 has a width, a length, and a height (e.g., athickness). The wicking pad 102 can be any size and shape. In certainembodiments, at least a section (e.g., the planar region 110 forapplying the substrate 112) of the wicking pad 102 is planar. In somecases, the length and the width of the wicking pad 102 are at leastabout 2-fold, 5-fold, 10-fold, 100-fold or more larger than the height(i.e., thickness).

Exemplary sizes for wicking pads include, without limitation, wickingpads that are at least about 0.25 cm, 0.5 cm, 1 cm, 2 cm, 3 cm, 4 cm, 5cm, 6 cm, 7 cm, 8 cm, 10 cm, 12 cm, 15 cm, 20 cm, 25 cm, 30 cm or morein at least one dimension. In some cases, the wicking pad 102 is 20±0.5,1, 2, 3, 4, 5, 6, 9 or 10 cm in length by 10±0.5, 1, 2, 3, 4, 5, 6, 7,8, or 9 cm in width.

The wicking pad 102 is an absorbent material. In some embodiments, thewicking pad 102 is configured to have a high solution capacity and alateral flow rate. In some cases, the high solution capacity and lateralflow rate are provided by having a wicking pad 102 with substantialheight (e.g., thickness). In some cases, the wicking pad 102 is about10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.75, 0.5, or about 0.2 mm thick. In somecases, the wicking pad 102 is between about 0.05 mm and about 0.5 mmthick.

In some embodiments, the wicking pad 102 has one or more reagents (e.g.,binding agents BA1, BA2, BA3 in FIG. 15 ) immobilized or embeddedtherein in one or more zones (e.g., in one or more zones downstream fromthe reservoirs 116 or in a zone inside each of the reservoirs 116). Theembedded reagents are generally embedded or bound and dried into thewicking pad such that the reagents remain immobile during fluid flow orsuch that the reagent are immobile until contacted by an aqueous fluidfront under lateral flow and are released at a user-defined event. Thezones can be printed lines or spots of reagent.

The wicking pad 102 generally has a large surface area due to thepresence of a plurality of pores. The large surface area can increasethe loading capacity of the wicking pad 102 for one or more reagents orone or more solutions containing a reagent. In some embodiments, thewicking pad 102 has a specific surface area of at least about 0.001m²/g, 0.02 m²/g, 0.1 m²/g, 0.5 m²/g, 1 m²/g, 10 m²/g, or more asmeasured by standard techniques.

In some embodiments, the wicking pad 102 can have a particular poresize, a particular average pore size, or a particular pore size range.For example, the wicking pad 102 can contain 0.1 μm pores, 0.2 μm pores,0.45 μm pores, or 1, 2, 4, 5, 6, 7, 8, 10, 15, 20 μm pores, or poreslarger than about 20 μm. As another example, the wicking pad 102 cancontain pores that average 0.1, 0.2, 0.45, 1, 2, 4, 5, 6, 7, 8, 10, 15,or 20 μm, or more in size. As another example, the wicking pad 102 cancontain pores that range about 0.1-8 μm, 0.2-8 μm, 0.45-8 μm, 1-8 μm,0.1-4 μm, 0.1-2 μm, 0.1-1 μm, 0.1-0.45 μm, 0.2-8 μm, 0.2-4 μm, 0.2-2 μm,0.2-1 μm, 0.2-0.45 μm, 0.45-8 μm, 0.45-4 μm, 0.45-2 μm, 0.45-1 μm, insize. In some cases, the wicking pad 102 can contain pores that are lessthan about 20 μm in size. For example, the wicking pad 102 can becomposed of a material in which at least about 50%, 60%, 70%, 80%, 90%or more of the pores are less than about 20, 15, 10, or 5 μm in size. Insome cases, the pores in the wicking pad 102 are large enough to containone or more proteins of average size (e.g., about 1 nm). For example,the pores can be at least 1 nm in size, at least 5 nm in size, at least10, 100, or 500 nm in size. Alternatively, at least 50%, 60%, 70%, 80%,90% or more of the pores can be more than 1, 5, 10, 50, 100, or 500 nmin size. As used herein, pore size can be measured as a radius or adiameter. In some cases, the wicking pad 102 contains porouspolyethylene, such as porous polyethylene having a pore size between 0.2and 20 microns, or between 1 and 12 microns. The wicking pad 102 canhave a different pore size in different regions of the pad. For example,the wicking pad 102 can have a lateral flow region that has a differentpore size or pore size range. In some embodiments, pore size is chosento control flow rate. For example, a larger pore size will allow for afaster flow rate.

The wicking pad 102 can be treated or functionalized to minimizenon-specific reagent binding, increase lateral flow, increase wicking,or to reduce protein aggregation. For example, the wicking pad 102, or aportion thereof, can be treated to alter the hydrophilicity or alter thehydrophobicity of the treated area. In some cases, altering thehydrophilicity or hydrophobicity of the wicking pad 102 can increasebinding agent loading, decrease binding agent aggregation ordenaturation, create mask regions in which binding agent is excludedfrom or not loaded, or direct flow of binding agents when the wickingpad is wet. In some cases, the wicking pad contains a proteinaggregation modifying agent as described herein.

The wicking pad 102, and the pump are generally formed of a bibulousmaterial and can be made out of, for example, natural fibers, syntheticfibers, glass fibers or blends thereof. Non-limiting examples includecotton, glass, and combinations thereof. There are many commercialmaterials available for diagnostic uses from vendors including, but notlimited to, Ahlstrom, GE, PALL, Millipore, Sartorius, and S&S.

The pump is formed from material having a liquid absorbing capacity thatis significantly greater than the wicking pad 102. In some embodiments,the pump is formed from one or more absorbent pads.

The bibulous material can include, but is not limited to, polymercontaining material. The polymer can be in the form of polymer beads, apolymer membrane, or a polymer monolith. In some cases, the polymer iscellulose. Cellulose containing pads include paper, cloth, woven, ornon-woven cellulose substrates. Cloth pads include those containing anatural cellulose fiber such as cotton or wool. Paper pads include thosecontaining natural cellulose fiber (e.g., cellulose or regeneratedcellulose) and those containing cellulose fiber derivatives including,but not limited to cellulose esters (e.g., nitrocellulose, celluloseacetate, cellulose triacetate, cellulose proprionate, cellulose acetatepropionate, cellulose acetate butyrate, and cellulose sulfate) andcellulose ethers (e.g., methylcellulose, ethylcellulose, ethyl methylcellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose,hydroxypropyl methyl cellulose, ethyl hydroxyethyl cellulose, andcarboxymethyl cellulose). In some cases, the cellulose pads containsrayon. In some cases, the pad is paper, such as a variety of WHATMAN®paper.

The bibulous material can also include, but is not limited to, asintered material. For example, the bibulous material can contain asintered glass, a sintered polymer, or sintered metal, or a combinationthereof. In some cases, the sintered material is formed by sintering oneor more of powdered glass, powdered polymer, or powdered metal. In othercases, the sintered material is formed by sintering one or more ofglass, metal, or polymer fibers. In still other cases, the sinteredmaterial is formed from the sintering of one or more of glass, polymer,or metal beads.

The bibulous material can also contain, but is not limited to, one ormore non-cellulosic polymers, e.g. a synthetic polymer, a naturalpolymer, or a semisynthetic polymer. For example, the material cancontain a polyester, such as polyglycolide, polylactic acid,polycaprolactone, polyethylene adipate, polyhydroxylalkanoate,polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyvalerate,polyethylene terephthalate, polybutylene terephthalate, polytrimethyleneterephthalate, polyethylene naphthalate, Vectran®. In some cases, thepolymer is spunbound, such as a spunbound polyester.

Additional synthetic polymers include, but are not limited to nylon,polypropylene, polyethylene, polystyrene, divinylbenzene, polyvinyl,polyvinyl difluoride, high density polyvinyl difluoride, polyacrylamide,a (C₂-C₆) monoolefin polymer, a vinylaromatic polymer, avinylaminoaromatic polymer, a vinylhalide polymer, a (C₁-C₆) alkyl(meth)acrylate polymer, a(meth)acrylamide polymer, a vinyl pyrrolidonepolymer, a vinyl pyridine polymer, a (C₁-C₆) hydroxyalkyl (meth)acrylatepolymer, a (meth)acrylic acid polymer, an acrylamidomethylpropylsulfonicacid polymer, an N-hydroxy-containing (C₁-C₆) alkyl(meth)acrylamidepolymer, acrylonitrile or a mixture of any of the foregoing.

The substrate 112 is generally planar in shape and can be, for example,a membrane formed of nitrocellulose, polyvinylidene fluoride, nylon, orpolysulfone. Other materials from which the substrate 112 can be formedinclude, but are not limited to, glass, plastic, silicon, metal, and/ormetal oxide that is bare or is functionalized with polymers. Plasticmaterials from which the substrate 112 can be formed include, but arenot limited to, polyethylene terephthalate, polypropylene, polystyrene,and/or polycarbonate. Examples of polymers with which to functionalizethe surface of substrates formed from metal or metal oxide includeglycidoxypropyltriethoxysilane, poly-L-lysine, polybrene, polyethyleneglycol polymers, dextran polymer, aminopropylsilane, caroxysilane,hydrogels and polymer brushes, and/or self-assembled monolayers of e.g.functionalized alkyl thiols, dendrimers or oligonucleotides.

Exemplary bonding methods to bond all or portions of the wicking pad tothe base or cover of the device include, but are not limited to, bondingwith an adhesive, thermal bonding, and organic solvent bonding with orwithout pressure. In embodiments using adhesive, the nature of theadhesive may affect the assay performance (i.e., flow characteristics,reagent stability) and can be optimized for the desired assay orapplication. In some embodiments, the adhesive may be part of the base114 of the device 100. Exemplary adhesives include, but are not limitedto, spray adhesive, ultraviolet light curable adhesive, or pressuresensitive adhesive.

In some embodiments, the base and/or the cover is formed from plasticincluding, but not limited to, polyethylene terephthalate,polypropylene, polystyrene, and polycarbonate. The base and/or covercan, for example, be vacuum or injection molded or otherwiseconstructed. In certain embodiments, the cover is fitted (e.g., snapfitted) to the base. In some embodiments, the cover is molded such thatthe cover contacts and exerts an even and downward force on the pumpwhen the cover is attached to the base. In certain embodiments, thecover is provided in more than one segment. For example, the cover caninclude a removable first segment, a second segment and a third segment.The first segment can cover the reservoirs, the second segment can coverthe substrate region, and the third segment can cover the pump of thedevice.

A. Exemplary Detection Reagents

i. Binding Agents

Binding agents are described herein for detection of analytes. In somecases, the binding agents are antibodies (e.g., primary or secondaryantibodies). Primary antibodies can be used to bind to an analyte. Insome cases, the primary antibody is labeled, enabling detection of theprimary antibody and subsequent detection of the analyte. In some cases,the primary antibody is detected by binding to a labeled secondarybinding agent, such as a labeled secondary antibody. In some cases,tertiary binding agents are utilized to detect complexes containing theanalyte and the primary and secondary binding agent.

Binding agents can be provided in one or more reagent solutions. Thereagent solutions can contain one of more buffers, salts, densityagents, or protein aggregation modifying agents as described herein.Density agents can be used to modulate the viscosity of the reagentsolution which will modulate the rate of solution flow out of thereservoirs. Having a density agent in each of the reagent solutions canalso enhance binding interactions between, e.g., the analytesimmobilized on the substrate and the binding agents (e.g., antibodies).Examples of density agents include, but are not limited to, glycerol,sucrose, trehalose, dextran, and polyethylene glycol. The bindingagent(s) can be stored in solution for at least about a day, three days,7-10 days, at least about a month, two months, 3 months, six months, ayear or longer.

Binding agents can also be provided on or in the wicking pad. Forexample, as illustrated in FIG. 15 , lines or spots of binding agentscan be immobilized in/on the wicking pad downstream from the reservoir(e.g., in planar region 110). In some embodiments, a first binding agentBA1 is a reversibly immobilized labeled first primary antibody (e.g., aprimary antibody conjugate) for detection, a second binding agent BA2 isan irreversibly immobilized unlabeled second primary antibody (e.g., a“test” primary antibody) for capture, and a third binding agent BA3 is acontrol antibody that binds to the first primary antibody. The controlantibody can be used to assess assay validity. In certain embodiments,the labeled first primary antibody is paired with the second primaryantibody and the two antibodies bind to different epitopes on theanalyte in such a way that the analyte, if present, is sandwiched inbetween the first primary antibody and second primary antibody duringthe lateral flow assay. In some embodiments, multiple matched pairs offirst and second primary antibodies are immobilized on the wicking padto allow for multiplex detection of analytes in the sample.

In some cases, a planar region of the wicking pad in fluid communicationwith fluid in one or more reservoirs contains one or more binding agentsdried thereon. The dried binding agent(s) can be reconstituted bycontacting the planar region of the wicking pad with an aqueoussolution. In some cases, the aqueous reconstitution buffer can containone or more re-wetting reagents including salts, buffers, or a proteinaggregation modifying agent as described herein. In some cases, thebinding agent (s) can be stored dry or substantially dry in the wickingpad for at least about a day, three days, 7-10 days, at least about amonth, two months, 3 months, six months, a year or longer.

ii. Labels

Analytes can be detected by detecting a label that is linked to abinding agent. The label can be linked directly to the binding agent(e.g., by a covalent or other bond to the primary antibody) or theattachment can be indirect (e.g., using a chelator or linker molecule).The terms “label” and “detectable label” are used synonymously herein.In some embodiments, each label (e.g., a first label linked to a firstbinding agent, a second label linked to a second binding agent, etc.)generates a detectable signal and the signals (e.g., a first signalgenerated by the first label, a second signal generated by the secondlabel, etc.) are distinguishable. In some embodiments, the two or morebinding agent labels comprise the same type of agent (e.g., a firstlabel that is a first fluorescent agent and a second label that is asecond fluorescent agent). In some embodiments, the two or more bindingagent labels (e.g., the first label, second label, etc.) combine toproduce a detectable signal that is not generated in the absence of oneor more of the labels.

Examples of detectable labels include, but are not limited to,biotin/streptavidin labels, nucleic acid (e.g., oligonucleotide) labels,chemically reactive labels, fluorescent labels, enzyme labels,radioactive labels, quantum dots, polymer dots, mass labels, colloidalgold, electrochemical labels and combinations thereof. In someembodiments, the label can include an optical agent such as achromophore, fluorescent agent, phosphorescent agent, chemiluminescentagent, or an electrochemiluminescent agent. Numerous agents (e.g., dyes,probes, or indicators) are known in the art and can be used in thepresent invention. (See, e.g., Invitrogen, The Handbook—A Guide toFluorescent Probes and Labeling Technologies, Tenth Edition (2005)).Chromophores include co-enzymes or co-factors that have a detectableabsorbance. In some cases, a binding agent can be detected by detectingthe intrinsic absorbance of a peptide bond at 220 nm or the compositeamino acid absorbance at 280 nm.

Fluorescent agents can include a variety of organic and/or inorganicsmall molecules or a variety of fluorescent proteins and derivativesthereof. For example, fluorescent agents can include but are not limitedto cyanines, phthalocyanines, porphyrins, indocyanines, rhodamines,phenoxazines, phenylxanthenes, phenothiazines, phenoselenazines,fluoresceins (e.g., FITC, 5-carboxyfluorescein, and6-carboxyfluorescein), benzoporphyrins, squaraines, dipyrrolopyrimidones, tetracenes, quinolines, pyrazines, corrins, croconiums,acridones, phenanthridines, rhodamines (e.g., TAMRA, TMR, and RhodamineRed), acridines, anthraquinones, chalcogenopyrylium analogues, chlorins,naphthalocyanines, methine dyes, indolenium dyes, azo compounds,azulenes, azaazulenes, triphenyl methane dyes, indoles, benzoindoles,indocarbocyanines, benzoindocarbocyanines, BODIPY™ and BODIPY™derivatives, and analogs thereof. In some embodiments, a fluorescentagent is an Alexa Fluor dye, a DyLight dye, or an IRDye. In someembodiments, a fluorescent agent is a polymer dot or a quantum dot.Fluorescent dyes and fluorescent label reagents include those which arecommercially available, e.g., from Invitrogen/Molecular Probes (Eugene,Oreg.), Pierce Biotechnology, Inc. (Rockford, Ill.), and LicorBiosciences (Lincoln, Nebr.). In some embodiments, the optical agent isan intercalating dye. In some embodiments, 2, 3, 4, 5, or more bindingagents are each labeled with an optical agent such as a fluorescentagent (e.g., a first binding agent labeled with a first fluorescentlabel, a second binding agent labeled with a second fluorescent label,etc.), and each binding agent that is labeled with an optical agent isdetected by detecting a signal generated by the optical agent (e.g., afluorescent signal generated by a fluorescent label). In someembodiments, the second fluorescent label quenches a fluorescent signalgenerated by the first fluorescent label. In some embodiments, the firstand second fluorescent labels are members of a fluorescence resonanceenergy transfer (FRET) pair. The term “fluorescence resonance energytransfer” or “FRET” refers to a transfer of energy between at least twochromophores, a donor chromophore and an acceptor chromophore. Typicallyin FRET, if the donor and acceptor are in sufficiently close proximity,the donor transfers its energy to the acceptor when the donor is excitedby light radiation with a suitable wavelength. The acceptor can re-emitthe transferred energy in the form of light radiation with a differentwavelength. Suitable FRET pairs (donor/acceptor) include, but are notlimited to, EDANS/fluorescein, IAEDANS/fluorescein,fluorescein/tetramethylrhodamine, fluorescein/LC Red 640, fluorescein/Cy5, fluorescein/Cy 5.5, and fluorescein/LC Red 705.

In some embodiments, all of the binding agents are labeled with anoptical agent, and each optical agent-labeled binding agent is detectedby detecting a signal generated by the optical agent.

In some embodiments, the label is a radioisotope. Radioisotopes includeradionuclides that emit gamma rays, positrons, beta and alpha particles,and X-rays. Suitable radionuclidesl include but are not limited to²²⁵Ac, ⁷²As, ²¹¹At, ¹¹B, ¹²⁸Ba, ²¹²Bi, ⁷⁵Br, ⁷⁷Br, ¹⁴C, ¹⁰⁹Cd, ⁶²Cu,⁶⁴Cu, ⁶⁷Cu, ¹⁸F, ⁶⁷Ga, ⁶⁸Ga, ³H, ¹⁶⁶Ho, ¹²³I, ¹²⁴I, ¹²⁵I, ¹³⁰I, ¹³¹I,¹¹¹In, ¹⁷⁷Lu, ¹³N, ¹⁵O, ³²P, ³³P, ²¹²Pb, ¹⁰³Pd, ¹⁸⁶Re, ¹⁸⁸Re, ⁴⁷Sc,¹⁵³Sm, ⁸⁹Sr, ^(99m)Tc, ⁸⁸Y and ⁹⁰Y. In some embodiments 2, 3, 4, 5, ormore binding agents are each labeled with a radioisotope (e.g., a firstbinding agent labeled with a first radioisotope, a second binding agentlabeled with a second radioisotope, etc.), and each binding agent thatis labeled with a radioisotope is detected by detecting radioactivitygenerated by the radioisotope. For example, one binding agent can belabeled with a gamma emitter and one binding agent can be labeled with abeta emitter. Alternatively, the binding agents can be labeled withradionuclides that emit the same particle (e.g., alpha, beta, or gamma)at different energies, where the different energies are distinguishable.In some embodiments, all of the binding agents are labeled with aradioisotope and each labeled binding agent can be detected by detectingradioactivity generated by the radioisotope.

In some embodiments, the label is an enzyme, and the binding agent isdetected by detecting a product generated by the enzyme. Examples ofsuitable enzymes include, but are not limited to, urease, alkalinephosphatase, (horseradish) hydrogen peroxidase (HRP), glucose oxidase,beta-galactosidase, luciferase, alkaline phosphatase, and an esterasethat hydrolyzes fluorescein diacetate. For example, ahorseradish-peroxidase detection system can be used with the chromogenicsubstrate tetramethylbenzidine (TMB), which yields a soluble product inthe presence of hydrogen peroxide that is detectable at 450 nm, or achemiluminescent substrate (e.g., Clarity from Bio-Rad Laboratories),which yields detectable light. An alkaline phosphatase detection systemcan be used with the chromogenic substrate p-nitrophenyl phosphate,which yields a soluble product readily detectable at 405 nm. Aβ-galactosidase detection system can be used with the chromogenicsubstrate o-nitrophenyl-β-D-galactopyranoside (ONPG), which yields asoluble product detectable at 410 nm. A urease detection system can beused with a substrate such as urea-bromocresol purple (SigmaImmunochemicals; St. Louis, Mo.). In some cases, the enzyme acts on afluorogenic substrate to generate a detectable fluorescent product. Insome embodiments, 2, 3, 4, 5, or more binding agents are each labeledwith an enzyme (e.g., a first binding agent labeled with a first enzyme,a second binding agent labeled with a second enzyme, etc.), and eachbinding agent that is labeled with an enzyme is detected by detecting aproduct generated by the enzyme. In some embodiments, all of the bindingagents are labeled with an enzyme, and each enzyme-labeled binding agentis detected by detecting a product generated by the enzyme.

In some embodiments, the label is an affinity tag. Examples of suitableaffinity tags include, but are not limited to, biotin, peptide tags(e.g., FLAG-tag, HA-tag, His-tag, Myc-tag, S-tag, SBP-tag, Strep-tag,eXact-tag), and protein tags (e.g., GST-tag, MBP-tag, GFP-tag).

In some embodiments, the label is a nucleic acid label. Examples ofsuitable nucleic acid labels include, but are not limited to,oligonucleotide sequences, single-stranded DNA, double-stranded DNA, RNA(e.g., mRNA or miRNA), or DNA-RNA hybrids. In some embodiments, thenucleic acid label is about 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70,80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900,or 1000 nucleotides in length. In some cases, the nucleic acid label isan amplified nucleic acid (e.g, by PCR or by isothermal polymeraseextension). In some cases, a label or labels are incorporated into anucleic acid label using a polymerase, reverse transcriptase, ligase, orother enzymes that act on nucleic acids (eg. fluorescently modifiednucleotides, biotin-nucleotides, digoxigenin-nucleotides, haptennucleotides). In some embodiments, the nucleic acid label is ligated toanother label (e.g., a nucleic acid) to create a detectable product(e.g, proximity ligation assays).

In some embodiments, the label is a nucleic acid barcode. As used hereina “barcode” is a short nucleotide sequence (e.g., at least about 4, 6,8, 10, or 12, nucleotides long) that uniquely defines a labeledmolecule, or a second molecule bound to the labeled binding agent. Thelength of the barcode sequence determines how many unique samples can bedifferentiated. For example, a 4 nucleotide barcode can differentiate 4⁴or 256 samples or less, a 6 nucleotide barcode can differentiate 4096different samples or less, and an 8 nucleotide barcode can index 65,536different samples or less. The use of barcode technology is well knownin the art, see for example Katsuyuki Shiroguchi, et al., “Digital RNAsequencing minimizes sequence-dependent bias and amplification noisewith optimized single-molecule barcodes”, PNAS 2012 Jan. 24;109(4):1347-52; and Smith, A M et al., “Highly-multiplexed barcodesequencing: an efficient method for parallel analysis of pooledsamples”, Nucleic Acids Research 2010 July; 38(13):e142.

In some embodiments, the label is a “click” chemistry moiety. Clickchemistry uses simple, robust reactions, such as the copper-catalyzedcycloaddition of azides and alkynes, to create intermolecular linkages.For a review of click chemistry, see Kolb et al., Agnew Chem40:2004-2021 (2001). In some embodiments, a click chemistry moiety(e.g., an azide or alkyne moiety) can be detected using anotherdetectable label (e.g., a fluorescently labeled, biotinylated, orradiolabeled alkyne or azide moiety).

Techniques for attaching detectable labels to binding agents such asproteins (e.g., antibodies) are well known. For example, a review ofcommon protein labeling techniques can be found in BiochemicalTechniques: Theory and Practice, John F. Robyt and Bernard J. White,Waveland Press, Inc. (1987). Other labeling techniques are reviewed in,e.g., R. Haugland, Excited States of Biopolymers, Steiner ed., PlenumPress (1983); Fluorogenic Probe Design and Synthesis: A Technical Guide,PE Applied Biosystems (1996); and G. T. Herman, Bioconjugate Techniques,Academic Press (1996).

In some embodiments, two or more labels (e.g., a first label, secondlabel, etc.) combine to produce a detectable signal that is notgenerated in the absence of one or more of the labels. For example, insome embodiments, each of the labels is an enzyme, and the activities ofthe enzymes combine to generate a detectable signal that is indicativeof the presence of the labels (and thus, is indicative of each of thelabeled proteins). Examples of enzymes combining to generate adetectable signal include coupled assays, such as a coupled assay usinghexokinase and glucose-6-phosphate dehydrogenase; and a chemiluminescentassay for NAD(P)H coupled to a glucose-6-phosphate dehydrogenase,beta-D-galactosidase, or alkaline phosphatase assay. See, e.g., Maeda etal., J Biolumin Chemilumin 1989, 4:140-148.

B. Protein Aggregation Modifying Agents

Described herein are protein aggregation modifying agents. Proteinaggregation modifying agents can be utilized to reduce or eliminateaggregation or denaturation of binding agents, such as proteins (e.g.,antibodies), stored in or delivered from a reagent solution, or thewicking pad 102. For example, protein aggregation modifying agents canbe utilized to reduce or eliminate aggregation or denaturation ofprimary antibodies stored in/delivered from the reagent solutions or thewicking pad 102. In some cases, protein aggregation modifying agents canbe utilized to facilitate lateral flow of binding agents in the planarregion 110 of the wicking pad 102.

In some cases, protein aggregation modifying agents that act to displaceproteins from the air-water interface and thereby protect them fromdenaturation and aggregation are particularly effective in reducing theaggregation of binding agents immobilized on the wicking pad 102. Inother cases, the protein aggregation modifying agent directly affectsthe stability of the binding agent by binding to the binding agentand/or stabilizing the binding agent. In other cases, the proteinaggregation modifying agent acts to shift the equilibrium away from adenatured or unfolded state and thus reduce aggregation. For example, insome cases, the interaction between the protein aggregation modifyingagent and the binding agent is thermodynamically disfavored due tostrong repulsion between an amide backbone of the binding agent and theprotein aggregation modifying agent. Thus, unfolding of the bindingagent in the presence of the protein aggregation modifying agent isdisfavored because unfolding exposes more amide backbone surface to theprotein aggregation modifying agent.

Protein aggregation modifying agents can be one or more of acyclodextrin, a non-ionic surfactant, an ionic surfactant, azwitterionic surfactant, a non-detergent sulfobetaine, a simple sugar, apolysaccharide, a polyol, an organic solvent, an aggregation modifyingprotein, a disordered peptide sequence, an amino acid, anoxido-reduction agent, a lyoprotectant, a cryoprotectant, or achaotropic agent.

Cyclodextrins can be, but are not limited to, α-cyclodextrin,β-cyclodextrin, γ-cyclodextrin, (2,3,6-tri-O-methyl)-β-cyclodextrin,(2,3,6-tri-O-methyl)-β-cyclodextrin, (2-hydroxy)propyl-β-cyclodextrin,(2-hydroxy)propyl-γ-cyclodextrin, random methyl-β-cyclodextrin, randommethyl-γ-cyclodextrin, carboxymethyl-β-cyclodextrin,carboxymethyl-γ-cyclodextrin, 6-monodeoxy-6-monoamino-β-cyclodextrin,sulfobutyl-β-cyclodextrin, 6-amino-6-deoxy-β-cyclodextrin, acetylβ-cyclodextrin, succinyl α-cyclodextrin, succinyl β-cyclodextrin,succinyl γ-cyclodextrin, (2,3,6-tri-O-benzoyl)-β-cyclodextrin,succinyl-(2-hydroxypropyl)-β-cyclodextrin, orsuccinyl-(2-hydroxypropyl)-γ-cyclodextrin. Cyclodextrins can also be acyclodextrin polymer containing one or more of the foregoingcyclodextrin molecules. Additional cyclodextrins are known in the art,and include, e.g. those described on the world wide web atcyclodextrin.com. Exemplary concentrations of cyclodextrins are, withoutlimitation, about 1 mM, 2 mM, 2.5 mM, 5 mM, 7.5 mM, 10 mM, 15 mM, 20 mM,25 mM, 50 mM, 75 mM, or 100 mM.

Non-ionic surfactants can be polyethylene-sorbitan-fatty acid esters,polyethylene-polypropylene glycols or polyoxyethylene-stearates.Polyethylene-sorbitan-fatty acid esters can bepolyethylene(20)-sorbitan-esters (Tween 20™) orpolyoxyethylene(20)-sorbitanmonooleate (Tween 80™).Polyethylene-polypropylene glycols can bepolyoxypropylene-polyoxyethylene block co-polymers such as those soldunder the names Pluronic® or Poloxamer™. Polyoxyethylene-stearates canbe, for example, those sold under the trademark Myrj™. Exemplary,polyoxyethylene monolauryl ethers include those sold under the trademarkBrij™, e.g., Brij-35. Exemplary concentrations of non-ionic surfactantsare, without limitation, about 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, 0.5%,0.75%, 1%, 2%, 2.5%, 5%, 7.5%, or about 10% w/w, w/v, or v/v.

Ionic surfactants can be anionic surfactants or cationic surfactants.Anionic surfactants useful in the present invention can be, but are notlimited to, soaps including alkali soaps, such as sodium, potassium orammonium salts of aliphatic carboxylic acids, usually fatty acids, suchas sodium stearate. Additional anionic surfactants include organic aminesoaps such as organic amine salts of aliphatic carboxylic acids, usuallyfatty acids, such as triethanolamine stearate. Cationic surfactantsuseful in the present invention include, but are not limited to, aminesalts such as octadecyl ammonium chloride or quarternary ammoniumcompounds such as benzalkonium chloride. Ionic surfactants can includethe sodium, potassium or ammonium salts of alkyl sulfates, such assodium dodecyl sulfate or sodium octyl sulfate. Exemplary concentrationsof ionic surfactants are, without limitation, about 0.01%, 0.02%, 0.05%,0.1%, 0.2%, 0.5%, 0.75%, 1%, 2%, 2.5%, 5%, 7.5%, or about 10% w/w, w/v,or v/v.

Zwitterionic surfactants have both cationic and anionic centers attachedto the same molecule. The cationic part is, e.g., based on primary,secondary, or tertiary amines or quaternary ammonium cations. Theanionic part can be a sulfonate, as in CHAPS(3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate). Otheranionic groups are sultaines illustrated by cocamidopropylhydroxysultaine or betaines, e.g., cocamidoethyl betaine, cocamidopropylbetaine, or lauramidopropyl betaine. Exemplary concentrations ofzwitterionic surfactants are, without limitation, about 0.01%, 0.02%,0.05%, 0.1%, 0.2%, 0.5%, 0.75%, 1%, 2%, 2.5%, 5%, 7.5%, and about 10%w/w, w/v, or v/v.

Non detergent sulfobetaines (NDSBs) have a sulfobetaine hydrophilicgroup and a short hydrophobic group that cannot aggregate to formmicelles, therefore NDSBs are not considered detergents. Exemplary NDSBsinclude, but are not limited to NDSB 256, NDSB 221, NDSB 211, NDSB 201,NDSB 195, 3-(4-tert-Butyl-1-pyridinio)-1-propanesulfonate,3-(1-pyridinio)-1-propanesulfonate, 3-(Benzyldimethylammonio)propanesulfonate, or Dimethylethylammoniumpropane sulfonate. Exemplaryconcentrations of NDSBs include, but are not limited to about 0.01%,0.02%, 0.05%, 0.1%, 0.2%, 0.5%, 0.75%, 1%, 2%, 2.5%, 5%, 7.5%, and about10% w/w, w/v, or v/v.

Polyols are compounds with multiple hydroxyl functional groups. In somecases, polyols can modify the aggregation or denaturation behavior of aprotein by a variety of mechanisms. For example, in some cases, thepolyol can shift the equilibrium to the folded state by presenting athermodynamically disfavored interaction with the protein backbone.Alternatively, in some cases, the polyol can bind to and stabilize thefolded state of the protein.

Polyols can be simple sugars such as sucrose, mannitol, sorbitol,inositol, xylitol, erythritol, glucose, galactose, raffinose, ortrehalose. Polyols can also be polysaccharides such as dextran, starch,hydroxyethyl starch, or polymers containing one or more of the simplesugars described herein. Glycerol, ethylene glycol, polyethylene glycol,pentaerythritol propoxylate, and pentaerythritol propoxylate, andcombinations thereof are also exemplary polyols.

Organic solvents can be, but are not limited to, those organic solventthat are known to inhibit denaturation, unfolding, or aggregation of oneor more proteins. A variety of suitable organic solvents are known inthe art. For example, organic solvents can include ethanol, butanol,propanol, phenol, dimethyl formamide, 2-methyl-2,4-pentanediol,2,3-butanediol, 1,2-propanediol, 1,6-hexanediol, or dimethyl sulfoxide.

Aggregation modifying proteins can be proteins known in the art toinhibit denaturation, unfolding, or aggregation of one or more proteins.Exemplary aggregation modifying proteins include, but are not limitedto, albumins, protein chaperones, and heat shock proteins. Albumins areproteins that are water-soluble, are moderately soluble in concentratedsalt solutions, and experience heat denaturation. Exemplary albuminsinclude serum albumins (e.g., bovine, horse, or human serum albumin) oregg albumin (e.g., hen egg-white albumin). Other exemplary aggregationmodifying proteins include casein, gelatin, ubiquitin, lysozyme, or lateembryogenesis abundant (LEA) proteins. LEA proteins include LEA I, LEAII, LEA III, LEA IV, LEA V, or atypical LEA proteins. LEA proteins areknown in the art and described, e.g., in Goyal K., et al., BiochemicalJournal 288(pt. 1), 151-57, (2005).

Protein aggregation modifying agents can also be amino acids. In somecases, the amino acids can serve an oxido-reduction function to maintainan appropriate oxidative potential for the protein immobilized on thesubstrate 112. Suitable oxido-reductive amino acids include cysteine andcystine. Other amino acids serve to reduce denaturation or aggregationthrough a non-oxido-reductive method. For example, arginine, glycine,proline, and taurine have been shown to reduce protein aggregation.

Other oxido-reduction agents can be employed to reduce proteinaggregation. Oxido-reductants other than cysteine and cystine, can beused to optimize the reduction potential in the substrate 112 onto whichthe protein is immobilized. Exemplary oxido-reductants includemercaptoethanol, dithiothreitol, dithioerythritol,tris(2-carboxyethyl)phosphine, glutathione, glutathione disulfide, andoxidized derivatives thereof, as well as Cu²⁺.

Protein aggregation modifying agents can also include lyoprotectants,cryoprotectants, or chaotropic agents. In some cases, the proteinaggregation modifying agent is a chaotrope such as urea, thiourea,guanidinium, cyanate, thiocyanate, trimethylammonium,tetramethylammonium, cesium, rubidium, nitrate, acetate, iodide,bromide, trichloroacetate, or perchlorate. Under certain conditions,such as at low concentrations, chaotropes can reduce proteinaggregation. Other protein aggregation modifying agents includetrimethylamine N-oxide.

Protein aggregation modifying agents can be salts. Exemplary saltsinclude, but not limited to, the sodium, potassium, magnesium, orcalcium salts of chloride, sulfate, or phosphate. Protein aggregationmodifying agents can also be buffering agents. Exemplary bufferingagents include, but are not limited to, tris (hydroxymethyl) aminomethene (TRIS), TAPSO, IVIES, HEPES, PIPES, CAPS, CAPSO, MOPS, MOPSO, orsodium or potassium phosphate, carbonate, bicarbonate, citrate, acetate,or borate buffers.

The protein aggregation modifying agents can be provided in any suitableconcentration. In some cases, the protein is provided as an aqueoussolution containing binding agent and protein aggregation modifyingagents. In such cases, the solution can be contacted with the wickinglayer and, optionally, dried. Exemplary concentrations of proteinaggregation modifying agents in the aqueous binding agent solutioninclude, but are not limited to, about 0.001%, 0.005%, 0.01%, 0.05%,0.1%, 0.5%, 1%, 2%, 4%, 5%, 10%, 20%, or about 25% or more w/v of thesolution. Further exemplary concentrations include, but are not limitedto, about 1 μM, 5 μM, 10 μM, 25 μM, 50 μM, 75 μM, 100 μM, 150 μM, 200μM, 300 μM, 500 μM, 750 μM, 1 mM, 5 mM, 10 mM, 25 mM, 50 mM, 100 mM, 150mM, 200 mM, 300 mM, 500 mM, and 1M.

In some cases, the protein aggregation modifying agents are provided inthe reagent solution. Exemplary compositions containing a proteinaggregation modifying agent contain about 0.001%, 0.005%, 0.01%, 0.05%,0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or about 10%, 20%, or about 25% byweight of one or more protein aggregation modifying agents.

Protein aggregation modifying agents can be provided in any suitablecombination. For example, in some cases, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10or more of the foregoing protein aggregation modifying agents can beutilized to reduce aggregation of a binding agent reversibly immobilizedon the wicking pad. In some cases, prior to contacting the wicking padwith the binding agent solution, the wicking pad contains a proteinaggregation modifying agent, and the binding agent solution contains thesame, or a different, protein aggregation modifying agent. In somecases, prior to contacting the wicking pad with the binding agentsolution, the wicking pad contains a protein aggregation modifyingagent, and the binding agent solution does not contain a proteinaggregation modifying agent. In some cases, prior to contacting thewicking pad with the binding agent solution, the binding agent solutioncontains a protein aggregation modifying agent and the wicking pad, orthe region to be contacted, does not.

III. METHODS

Provided are methods of performing a lateral flow assay using thedevices described herein. In an embodiment, the method comprisescontacting a substrate 112 (e.g., a Western blot) having immobilizedanalytes or binding agent(s) with the wicking pad 102, which can besupplied pre-moistened or can be pre-moistened by the user with, forexample, lateral flow buffer. In some embodiments (FIGS. 1-10 ), thesubstrate 112 is placed face down on the wicking pad 102 downstream fromthe reservoirs and upstream from the pump 120 (e.g., between thereservoirs and the pump or in the region 110 of the wicking pad 102). Insome embodiments, the substrate is placed on the base such that when acover is placed onto the device, the wicking pad contacts the substrate112 in the region 110 of the wicking pad and the substrate 112 ispositioned face up relative to the base (FIGS. 11-14 ).

In embodiments having the wicking pad bonded at least in part to thebase (FIGS. 1-10 ), a different reagent solution is next applied to eachof the reservoirs. The reagent solutions can also be applied to thereservoirs in any order. In some embodiments, the reagent solutions areapplied to the reservoirs starting with a first reservoir R1 closest tothe region 110 for contacting the substrate 112. The reagent solutionscan be applied to the reservoirs sequentially or simultaneously. Inembodiments having the wicking pad bonded at least in part to the cover(FIGS. 11-14 ), the different reagent solutions can be applied to eachof the reservoirs before or after the cover is placed on the device. Inembodiments in which the reagent solutions are applied to the reservoirsafter the cover is placed on the device, the solutions can be appliedthrough one or more ports or holes in the device. In an embodiment, fourdifferent reagent solutions (e.g., primary antibody, first washsolution, secondary antibodies or secondary detection reagents, andsecond wash solution) are applied to the reservoirs. In embodimentshaving two or more sets of reservoirs (FIG. 16 ), a different or thesame set of four reagent solutions is applied to each set of reservoirs,depending on the analytes or binding agents immobilized on the substrate112.

In some embodiments, a first reagent solution having labeled primaryantibody is applied to a first reservoir R1 and a second reagentsolution having a first wash solution is applied to a second reservoirR2. In certain embodiments, four different reagent solutions are appliedto the reservoirs in the following order: the first reagent solutionhaving primary antibody is applied to the first reservoir R1, the secondreagent solution having a first wash solution is applied to the secondreservoir R2, a third reagent solution having a secondary antibody or asecondary detection reagent is applied to a third reservoir R3, and afourth reagent solution having a second wash solution is applied to afourth reservoir R4. In some embodiments, four different reagentsolutions are applied to the reservoirs in the following order: thefourth reagent having the second wash solution is applied to the fourthreservoir R4, the second reagent solution having the first wash solutionis applied to the second reservoir R2, the first reagent solution havingprimary antibody is applied to the first reservoir R1, and the thirdreagent solution having a secondary antibody or a secondary detectionreagent is applied to the third reservoir R3. In certain embodiments,the second reagent solution is applied to the second reservoir R2 beforethe fourth reagent solution is applied to the fourth reservoir R4. Insome embodiments, the reagent solution applied to the reservoir has atleast twice the volume of another reagent solution. For example, thevolume of the second wash solution in the fourth reservoir R4 can be atleast twice the volume of the secondary antibody in the third reservoirR3. In some embodiments, the fourth reagent solution having the secondwash solution is omitted to allow the secondary antibody or secondarydetection reagent in the third reservoir R3 more time to bind to theprimary antibody.

In an embodiment in which the substrate has immobilized binding agentsthereon, a sample with an analyte is applied to the first reservoir R1,a first wash solution is applied to the second reservoir R2, a secondarydetection reagent is applied to the third reservoir R3 and, if needed, asecond wash solution is applied to the fourth reservoir R4.

In some embodiments in which there is no substrate 112 and in whichbinding agents are immobilized in lines or spots on a planar region 100of the wicking pad 102 downstream from the reservoirs, a differentsolution (e.g., a sample or a reagent solution) is applied to at leasttwo of the reservoirs. Referring to FIG. 15 , in an embodiment in whicha line of labeled reversibly immobilized first primary antibodies (e.g,first binding agent BA1 or primary antibody conjugate), a line ofunlabeled irreversibly immobilized second primary antibodies (e.g.,second binding agent BA2 or test primary antibodies), and a line ofirreversibly immobilized control antibodies (e.g., third binding agentBA3) that bind to the first primary antibodies is printed on the planarregion 110 of the wicking pad 102, a sample having one or more analytesand optionally a control protein is applied to the first reservoir R1and a wash solution (e.g., lateral flow buffer) is applied to the secondreservoir R2. In some embodiments in which an unlabeled second primaryantibody and a control antibody are irreversibly immobilized on theplanar region 110 of the wicking pad 102, a detection reagent (e.g.,labeled primary antibody) is applied to the third reservoir R3 and, ifneeded, a second wash solution is applied to the fourth reservoir R4.

In an embodiment in which analytes are immobilized in lines or spots onthe planar region 110 of the wicking pad 102 downstream from thereservoirs, a labeled primary antibody is applied to the first reservoirR1 and a first wash solution is applied to the second reservoir R2. Ifneeded, a secondary detection reagent is applied to the third reservoirR3 and a second wash solution is applied to the fourth reservoir R4.

The reagent solutions and/or sample are then allowed to flowsequentially from the reservoirs onto the region 110 of the wicking pad102. In an embodiment having reagent immobilized in a zone of thewicking pad 102 inside one or more of the reservoirs, to initiatesequential flow of the reagents from the reservoirs to the wicking pad102, lateral flow (e.g., running) buffer is applied sequentially orsimultaneously to all of the reservoirs. In some cases, the lateral flow(e.g., the progress) of each of the reagent solutions out of thereservoirs 116 and into/through the wicking pad 102 is monitoredvisually with one or more dyes or indicators in each of the reagentsolutions.

In embodiments having analytes immobilized on the substrate 112, thereagent solutions are pulled by wicking from the reservoirs into thewicking pad and to the dry pump, carrying the reagents (e.g., theprimary antibody, the first wash solution, and if needed, secondaryantibodies and the second wash solution) in the reagent solutionssequentially by lateral flow into contact with the substrate 112 havingproteins or analytes immobilized thereon. The primary antibodies in thefirst reagent solution are transported in the wicking pad 102, contactthe proteins or analytes on the substrate 112, and bind to the targetproteins or analytes, if present, on the substrate 112. In someembodiments, lateral flow of the reagent solutions/lateral flow bufferfrom the reservoirs to the pump further allows the first wash solutionin the second reagent solution to be transported in the wicking pad 102such that unbound primary antibodies are removed from the substrate 112.In certain embodiments, lateral flow of the reagent solutions/lateralflow buffer from the reservoirs to the pump further allows the secondaryantibodies or a secondary detection reagent in the third reagentsolution to be transported in the wicking pad 102 and to contact theprimary antibodies bound to their target proteins, if present, on thesubstrate 112. In some embodiments, lateral flow of the reagentsolutions/lateral flow buffer from the reservoirs to the pump furtherallows the second wash solution in the fourth reagent solution to betransported in the wicking pad 102 such that unbound secondaryantibodies are removed from the substrate 112. In some embodiments, thevolume of the second wash solution applied to and transported in thewicking pad 102 is twice the volume of secondary antibody applied to andtransported in the wicking pad 102.

In embodiments in which binding agents are immobilized on the substrate112, the sample and reagent solutions are pulled by wicking from thereservoirs into the wicking pad and to the dry pump, carrying theanalytes (and optional control protein) in the sample and the reagents(e.g., the first wash solution, the secondary detection reagent and, ifneeded, the second wash solution) in the reagent solutions sequentiallyby lateral flow into contact with the substrate 112. In someembodiments, the sample is a biological sample. Biological samples canbe obtained from any biological organism, e.g., an animal, plant,fungus, bacterial, or any other organism. In some embodiments, thebiological sample is from an animal, e.g., a mammal (e.g., a human or anon-human primate, a cow, horse, pig, sheep, cat, dog, mouse, or rat), abird (e.g., chicken), or a fish. A biological sample can be any tissueor bodily fluid obtained from the biological organism, e.g., blood, ablood fraction, or a blood product (e.g., serum, plasma, platelets, redblood cells, and the like), sputum or saliva, tissue (e.g., kidney,lung, liver, heart, brain, nervous tissue, thyroid, eye, skeletalmuscle, cartilage, or bone tissue); cultured cells, e.g., primarycultures, explants, transformed cells, stem cells, stool, or urine. Insome embodiments, the sample includes a positive control protein forassessing assay validity or for normalizing the test signal across amultiplicity of different antibody zones.

In embodiments in which binding agents are immobilized on the region 110of the wicking pad downstream from the reservoirs, the sample andreagent solutions are pulled by wicking from the reservoirs into thewicking pad and to the dry pump, carrying the analytes in the sample andthe reagents (e.g., the first wash solution and, if needed, thesecondary detection reagent and the second wash solution) in the reagentsolutions sequentially by lateral flow into contact with the region 110.

In some embodiments, before or after initiating lateral flow and duringlateral flow, a substantially uniform pressure is applied to the pump toimprove contact of the pump with the wicking pad 102. For example, aweight can be placed on top of the pump or the cover (or a portion ofthe cover) can be attached to the base to urge the pump toward thewicking pad 102.

In embodiments having the wicking pad bonded at least in part to thebase, a cover can be placed onto the device once the reagent solutionshave been applied to the reservoirs to minimize evaporation and to applyeven pressure to the pump 120. The cover can be snap-fit onto the baseto apply even pressure or the cover can be placed loosely on top of thebase and then the base with the cover can be placed into a drawer-likecontainer that slides into a box. Prior to attaching the cover or inplace of the cover, a sponge can be placed on the pump to aide inapplying even pressure to the pump. The process requires minimal userinteraction with the consumable.

In some embodiments having a substrate, during lateral flow, the bindingof primary antibodies to the target proteins (and optionally contact ofsecondary antibodies or secondary detection reagents to the primaryantibody) is followed visually or by using a detector. In someembodiments, the substrate 112 is removed from the lateral flow device100 and the binding of the primary antibodies to the target proteins, ifpresent, is detected. In some embodiments, the antibody binding to thetarget protein is visualized and/or detected through the use ofdetectable moieties and/or labels as described herein. Suitable labelsand/or moieties are detected by spectroscopic, photochemical,biochemical, immunochemical, isotopic, electrical, optical, chemical, ormass spectrometric techniques.

In an embodiment in which binding agents are immobilized on the planarregion 110 of the wicking pad, during lateral flow, the binding of theanalyte, if present, to the first primary antibody and to the secondprimary antibody (e.g., detection of the analyte sandwiched between thefirst and second primary antibodies) is followed visually or by using adetector. In some embodiments, the binding of the analyte to the firstand second primary antibodies is visualized and/or detected through theuse of detectable moieties and/or labels as described herein.

There are many absorbent bibulous pad materials, wick pad materials, andantibody application materials known in the art, the selection fromwhich can be made to control the volume, to control the flow rate of thesystem, to ensure even flow, and to ensure complete delivery ofantibodies/reagents from the reservoirs. Other methods that affect thetiming of reagent/antibody delivery such as using torturous paths in thewick pad are possible. Still other embodiments to control the lateralflow process could be engineered into the plastic casing where thesurface may contain sloped regions to slow or speed the flow of liquidusing gravity (see FIGS. 2 and 3 ).

Shown in FIGS. 1-15 are consumable devices that hold a single mini-gelsized membrane. Often users run western blots using membranes termedmidi size blots which are typically 2× the width of a mini sizedmembrane. In other western blot applications the user may cut a miniand/or midi sized membrane into smaller sections that correspond to afew lanes of the original gel used for electrophoresis and transfer ofthe proteins. Therefore, the consumable lateral flow device could be ofa size to accommodate either a mini or midi-sized membrane in someembodiments. In still other embodiments there could be separate ridgesmolded into or otherwise present in the base of the consumable wheremembrane sections could be placed.

In other embodiments of the lateral flow device, multiple antibodies maybe mixed and loaded into one or more of the reservoirs to facilitatemultiplex detection of targets in a single sample.

IV. KITS

Kits for performing a lateral flow assay according to methods describedherein are provided. Also provided are kits containing lateral flowdevices as described herein. In some embodiments, the kit comprisesreagents (e.g., binding agents including labeled primary antibody orprimary and secondary antibodies, wash solution, and/or lateral flowbuffer) in liquid form (e.g., reagent solutions) that are applied to thedevice by the end-user. In some embodiments, solutions are provided in aconcentrated form (e.g., 5× or 10×) that is diluted prior to use. Insome embodiments, the reagents are provided in solid form that isreconstituted with liquid, e.g. buffer, prior to use.

In some embodiments, the kit contains blocking agents (e.g., bovineserum albumin and/or non-fat dried milk), surfactants (e.g., Tween 20 orTriton X-100), protein aggregation modifying agents as described herein,crowding agents (e.g., dextran, polyethylene glycol and/or Ficoll),density agents, and/or agents to promote even flow of reagents and/orpromote reaction to molecules on the substrate and minimize backgroundon the substrate. The additional agents can be provided in the kit as asolid (e.g., a powder) or in liquid form (e.g., as a solution). In someembodiments, the kit further comprises instructions for carrying out themethods described herein.

IV. EXAMPLES Example 1—Sequential Lateral Flow of Solutions fromReservoirs

This example illustrates the sequential lateral flow of coloredsolutions from reservoirs in a lateral flow device as depicted in FIGS.4A and 4B.

In FIG. 17A, the wick pad (glass fiber) was wet first with lateral flowbuffer (1% casein, 1×PBS Buffer, 0.1% Tween 20), a pump (not shown inFIGS. 17A-17E, see FIG. 4A) was placed on the right side of the device.Yellow and blue dye solutions were made by adding Orange G (Sigma) orXylene Cyanol (Bio-Rad) to lateral flow buffer. Alternating yellow andblue solutions were placed into reservoirs R1, R2, R3 and R4. Solution 1in reservoir 1 flowed into and was completely drained into the wickingpad as the solution 1 was drawn to the pump (FIG. 17B). While thesolution 1 was flowing into the wicking pad, the solutions 2, 3, and 4in the other reservoirs did not move nor mix. As shown in FIG. 17C,after solution 1 was completely drained from the reservoir 1, thesolution 2 in Reservoir 2 migrated by lateral flow out of Reservoir 2through the wick material, across the upstream wall of Reservoir 1 andup the downstream wall in its flow course to the pump. Again, thesolutions remaining in the reservoirs most distant to the pump (R3 andR4) did not empty or mix. Once the solution 2 was completely drainedfrom the reservoir 2, the liquid in the reservoir 3 was then drained bythe pump (FIG. 17D). Lastly, as shown in FIG. 17E, the solution inReservoir 4 was partially depleted as the solution flowed to the pump.After some time, the Reservoir 4 was completely drained (not shown).

The results show that the lateral flow devices described herein candeliver solutions sequentially to a wicking pad.

Example 2—Detection of hRAS, PCNA and PARP from HEK293 Cell Lysate

This example illustrates the use of lateral flow devices as depicted inFIGS. 4A and 4B and as described herein to perform western blot assays.

Lyophilized HEK293 protein lysate (Bio-Rad Laboratories PrecisionAbcontrol lysate VLY002) was reconstituted in 1× Laemmli sample buffercontaining 40 mM DTT and denatured by heating at 100° C. for 5 min. Aseries of two-fold dilutions of the lysate (20 ug down to 0.04 ug) wasloaded onto 4-20% TGX mini gels (Bio-Rad Laboratories) andelectrophoresed at 250V for 25 min. Each gel was transferred to a PVDFmembrane using the Transblot Turbo device (Bio-Rad) and prepackedtransfer packs using a setting of 2.5 A×7 min per two gels. Followingtransfer, the membranes were quickly rinsed in 1×PBS buffer (10 mMsodium phosphate, 150 mM NaCl, pH 7.4) and then placed in a lateral flowbuffer containing 1% casein, 1×PBS Buffer, 0.1% Tween 20, and placed ona rocker for 10 minutes to block. While the membranes were incubating inlateral flow buffer, three primary antibody solutions were prepared at a1:1000 dilution by mixing 3 μl of (1) mouse anti-hRAS monoclonal Ab(Bio-Rad Laboratories, #VMA00040), (2) mouse anti-PCNA monoclonal Ab(Bio-Rad Laboratories, #VMA00018), and (3) mouse anti-PARP monoclonal Ab(Bio-Rad Laboratories, #VMA00016) into 3 ml of lateral flow buffer.Secondary antibody (goat anti-mouse IgG-HRP antibody conjugate, Bio-RadLaboratories #STAR207P) was prepared at a 1:1000 dilution in lateralflow buffer.

Blot detection was performed as follows. A glass fiber wick pad(Ahlstrom) was cut to 8.4 cm×21 cm and thermally bonded to the v-shapedcontour of the tray during the vacuum molding process as shown in FIGS.4A and 4B. Nine layers of thick blot paper ˜4.3 cm×9.5 cm (Bio-Rad) wereplaced on one end of the wick pad to serve as the pump. The glass fiberwick pad was wet with 7 ml of lateral flow buffer. The membrane wasremoved from blocking solution, and placed inverted (antigen side down)onto the wicking pad with the low molecular weight proteins nearest thepump; bubbles were removed by rolling. A 0.7 kg mass was placed atop thepump to ensure uniform contact with the wicking pad, and then thetroughs, as numbered in FIGS. 17A-17E, were immediately filled withreagent solutions (Reservoir 1: 3 ml of primary antibody; Reservoir 2: 3ml of lateral flow buffer; Reservoir 3: 2 ml of secondary antibody; andReservoir 4: 8 ml of lateral flow buffer). The lateral flow devices wereleft on a level surface at room temperature undisturbed until all thereservoirs were drained of liquid.

After 4 hours, the membranes were removed from the lateral flow devicesand washed 2×5 minutes in water. Detection of the binding reactionbetween the antigens and binding agents was performed using Claritychemiluminescent substrate (Bio-Rad Laboratories) per the instructions.FIGS. 18A, 18B and 18C are images of the three blot membranescorresponding to the three antigens (hRAS, PCNA, and PARP) tested. Theimages shown in FIGS. 18A-18C were acquired using Bio-Rad's Chemidoc MPimager using exposure times of 14 seconds for FIG. 18A, 1 second forFIG. 18B, and 46 seconds for FIG. 18C. The images show that all threetarget antigens were detected at multiple dilutions of the HEK293 celllysate.

The results show that the lateral flow devices described herein candeliver western blotting reagents (e.g., specific binding agents,lateral flow buffer, wash solutions) sequentially and without userintervention to a blot on a wicking pad.

All patents, patent applications, and other published referencematerials cited in this specification are hereby incorporated herein byreference in their entirety.

What is claimed is:
 1. A lateral flow device comprising: a wicking padcomposed of a porous material, the wicking pad having a planar regioncomprising immobilized binding agents; and wherein the wicking pad has afirst end, a second end and two lateral edges; a base comprising two ormore reservoirs having top openings and that are spatially separatedfrom each other by reservoir walls, wherein each of the reservoirsreceives and is in fluid communication with the first end of the wickingpad, wherein the first end of the wicking pad is received from the topopenings of each reservoir and passes over the reservoir walls; and apump comprising an absorbent pad contacting the second end of thewicking pad.
 2. The device of claim 1, wherein each of the reservoirs isa depression.
 3. The device of claim 1, wherein a longest dimension ofeach of the reservoirs is perpendicular to the lateral edges of thewicking pad.
 4. The device of claim 1, wherein a cross-section of eachof the reservoirs has a shape selected from the group consisting of a v,a semicircle, an oval, a u, a rectangle, a square, and a trapezoid. 5.The device of claim 1, wherein the reservoirs are attached to each otheron at least one side.
 6. The device of claim 1, wherein the reservoirsare formed from molded plastic.
 7. The device of claim 6, wherein theplastic is selected from the group consisting of polyethyleneterephthalate, polyethylene terephthalate glycol-modified,polypropylene, polystyrene, and polycarbonate.
 8. The device of claim 1,wherein at least a part of the wicking pad is bonded to the base.
 9. Thedevice of claim 1, wherein the wicking pad or the pump is formed of atleast one absorbent material selected from the group consisting of glassfiber, cotton, cellulose, a cellulose fiber derivative, sintered glass,sintered polymer, sintered metal, and a synthetic polymer.
 10. Thedevice of claim 1, wherein the wicking pad and the pump are dry.
 11. Thedevice of claim 1, wherein the wicking pad is wet.
 12. The device ofclaim 1, wherein the pump contacts an upper surface or a lower surfaceof the second end of the wicking pad.
 13. The device of claim 1, whereinthe device further comprises a cover.
 14. The device of claim 13,wherein at least a part of the wicking pad is bonded to the cover. 15.The device of claim 13, wherein the cover comprises at least twoprojections each of which project into a different reservoir.
 16. Thedevice of claim 15, wherein each of the projections is a blade spanningthe width of the reservoir into which the blade projects.
 17. The deviceof claim 15, wherein at least a portion of the wicking pad follows thecontours of and is bonded to each of the projections.
 18. The device ofclaim 15, wherein the wicking pad is not bonded to the base or the coverand wherein each of the projections urge portions of the wicking padinto a different reservoir when the cover is placed onto the device. 19.The device of claim 13, wherein at least two portions of the wicking padare formed into protrusions each of which project into a differentreservoir when the cover is placed onto the device.
 20. A method ofperforming a lateral flow assay, the method comprising; providing thedevice of claim 1; optionally applying a lateral flow buffer to thewicking pad; applying a different solution to at least two of thereservoirs starting with a reservoir closest to the planar region of thewicking pad comprising immobilized binding agents; and allowing lateralflow of the solutions from the reservoirs to the pump such that thesolutions are sequentially transported in the wicking pad and arecontacted to the binding agents immobilized on the wicking pad.